{"dataType": "CVE_RECORD", "cveMetadata": {"cveId": "CVE-2024-26804", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-02-19T14:20:24.179Z", "datePublished": "2024-04-04T08:20:31.305Z", "dateUpdated": "2025-05-04T12:54:46.707Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-05-04T12:54:46.707Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ip_tunnel: prevent perpetual headroom growth\n\nsyzkaller triggered following kasan splat:\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\n[..]\n kasan_report+0xda/0x110 mm/kasan/report.c:588\n __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\n skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\n ___skb_get_hash net/core/flow_dissector.c:1791 [inline]\n __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\n skb_get_hash include/linux/skbuff.h:1556 [inline]\n ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\n ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\n dev_queue_xmit include/linux/netdevice.h:3134 [inline]\n neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\n ...\n ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\n ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\n ..\n iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\n ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\n ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n ...\n\nThe splat occurs because skb->data points past skb->head allocated area.\nThis is because neigh layer does:\n  __skb_pull(skb, skb_network_offset(skb));\n\n... but skb_network_offset() returns a negative offset and __skb_pull()\narg is unsigned.  IOW, we skb->data gets \"adjusted\" by a huge value.\n\nThe negative value is returned because skb->head and skb->data distance is\nmore than 64k and skb->network_header (u16) has wrapped around.\n\nThe bug is in the ip_tunnel infrastructure, which can cause\ndev->needed_headroom to increment ad infinitum.\n\nThe syzkaller reproducer consists of packets getting routed via a gre\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\ntunnel.  The ipip encapsulation finds gre0 as next output device.\n\nThis results in the following pattern:\n\n1). First packet is to be sent out via gre0.\nRoute lookup found an output device, ipip0.\n\n2).\nip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the future\noutput device, rt.dev->needed_headroom (ipip0).\n\n3).\nip output / start_xmit moves skb on to ipip0. which runs the same\ncode path again (xmit recursion).\n\n4).\nRouting step for the post-gre0-encap packet finds gre0 as output device\nto use for ipip0 encapsulated packet.\n\ntunl0->needed_headroom is then incremented based on the (already bumped)\ngre0 device headroom.\n\nThis repeats for every future packet:\n\ngre0->needed_headroom gets inflated because previous packets' ipip0 step\nincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0\nneeded_headroom was increased.\n\nFor each subsequent packet, gre/ipip0->needed_headroom grows until\npost-expand-head reallocations result in a skb->head/data distance of\nmore than 64k.\n\nOnce that happens, skb->network_header (u16) wraps around when\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\nafter the headroom expansion/reallocation.\n\nAfter this skb_network_offset(skb) returns a different (and negative)\nresult post headroom expansion.\n\nThe next trip to neigh layer (or anything else that would __skb_pull the\nnetwork header) makes skb->data point to a memory location outside\nskb->head area.\n\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\nprevent perpetual increase instead of dropping the headroom increment\ncompletely."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/ipv4/ip_tunnel.c"], "versions": [{"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "f81e94d2dcd2397137edcb8b85f4c5bed5d22383", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "2e95350fe9db9d53c701075060ac8ac883b68aee", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "afec0c5cd2ed71ca95a8b36a5e6d03333bf34282", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "ab63de24ebea36fe73ac7121738595d704b66d96", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "049d7989c67e8dd50f07a2096dbafdb41331fb9b", "status": "affected", "versionType": "git"}, {"version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f", "status": "affected", "versionType": "git"}, {"version": "03017375b0122453e6dda833ff7bd4191915def5", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/ipv4/ip_tunnel.c"], "versions": [{"version": "2.6.34", "status": "affected"}, {"version": "0", "lessThan": "2.6.34", "status": "unaffected", "versionType": "semver"}, {"version": "5.4.271", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.212", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.151", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.81", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.21", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.7.9", "lessThanOrEqual": "6.7.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.8", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "5.4.271"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "5.10.212"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "5.15.151"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "6.1.81"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "6.6.21"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "6.7.9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.34", "versionEndExcluding": "6.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.33.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383"}, {"url": "https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee"}, {"url": "https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282"}, {"url": "https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96"}, {"url": "https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9"}, {"url": "https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b"}, {"url": "https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f"}], "title": "net: ip_tunnel: prevent perpetual headroom growth", "x_generator": 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"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-02T00:14:13.557Z"}}, {"title": "CISA ADP Vulnrichment", "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "LOW", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2024-26804", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2024-11-12T16:26:17.359512Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-416", "description": "CWE-416 Use After Free"}]}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-05-23T19:01:22.105Z"}}], "cna": {"title": "net: ip_tunnel: prevent perpetual headroom growth", "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "f81e94d2dcd2397137edcb8b85f4c5bed5d22383", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "2e95350fe9db9d53c701075060ac8ac883b68aee", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "afec0c5cd2ed71ca95a8b36a5e6d03333bf34282", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "ab63de24ebea36fe73ac7121738595d704b66d96", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "049d7989c67e8dd50f07a2096dbafdb41331fb9b", "versionType": "git"}, {"status": "affected", "version": "243aad830e8a4cdda261626fbaeddde16b08d04a", "lessThan": "5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f", "versionType": "git"}, {"status": "affected", "version": "03017375b0122453e6dda833ff7bd4191915def5", "versionType": "git"}], "programFiles": ["net/ipv4/ip_tunnel.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "2.6.34"}, {"status": "unaffected", "version": "0", "lessThan": "2.6.34", "versionType": "semver"}, {"status": "unaffected", "version": "5.4.271", "versionType": "semver", "lessThanOrEqual": "5.4.*"}, {"status": "unaffected", "version": "5.10.212", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.151", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.81", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.21", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.7.9", "versionType": "semver", "lessThanOrEqual": "6.7.*"}, {"status": "unaffected", "version": "6.8", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["net/ipv4/ip_tunnel.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383"}, {"url": "https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee"}, {"url": "https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282"}, {"url": "https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96"}, {"url": "https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9"}, {"url": "https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b"}, {"url": "https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ip_tunnel: prevent perpetual headroom growth\n\nsyzkaller triggered following kasan splat:\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\n[..]\n kasan_report+0xda/0x110 mm/kasan/report.c:588\n __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\n skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\n ___skb_get_hash net/core/flow_dissector.c:1791 [inline]\n __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\n skb_get_hash include/linux/skbuff.h:1556 [inline]\n ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\n ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\n dev_queue_xmit include/linux/netdevice.h:3134 [inline]\n neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\n ...\n ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\n ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\n ..\n iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\n ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\n ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n ...\n\nThe splat occurs because skb->data points past skb->head allocated area.\nThis is because neigh layer does:\n  __skb_pull(skb, skb_network_offset(skb));\n\n... but skb_network_offset() returns a negative offset and __skb_pull()\narg is unsigned.  IOW, we skb->data gets \"adjusted\" by a huge value.\n\nThe negative value is returned because skb->head and skb->data distance is\nmore than 64k and skb->network_header (u16) has wrapped around.\n\nThe bug is in the ip_tunnel infrastructure, which can cause\ndev->needed_headroom to increment ad infinitum.\n\nThe syzkaller reproducer consists of packets getting routed via a gre\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\ntunnel.  The ipip encapsulation finds gre0 as next output device.\n\nThis results in the following pattern:\n\n1). First packet is to be sent out via gre0.\nRoute lookup found an output device, ipip0.\n\n2).\nip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the future\noutput device, rt.dev->needed_headroom (ipip0).\n\n3).\nip output / start_xmit moves skb on to ipip0. which runs the same\ncode path again (xmit recursion).\n\n4).\nRouting step for the post-gre0-encap packet finds gre0 as output device\nto use for ipip0 encapsulated packet.\n\ntunl0->needed_headroom is then incremented based on the (already bumped)\ngre0 device headroom.\n\nThis repeats for every future packet:\n\ngre0->needed_headroom gets inflated because previous packets' ipip0 step\nincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0\nneeded_headroom was increased.\n\nFor each subsequent packet, gre/ipip0->needed_headroom grows until\npost-expand-head reallocations result in a skb->head/data distance of\nmore than 64k.\n\nOnce that happens, skb->network_header (u16) wraps around when\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\nafter the headroom expansion/reallocation.\n\nAfter this skb_network_offset(skb) returns a different (and negative)\nresult post headroom expansion.\n\nThe next trip to neigh layer (or anything else that would __skb_pull the\nnetwork header) makes skb->data point to a memory location outside\nskb->head area.\n\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\nprevent perpetual increase instead of dropping the headroom increment\ncompletely."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.4.271", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.212", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.151", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.81", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.21", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.7.9", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.8", "versionStartIncluding": "2.6.34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionStartIncluding": "2.6.33.2"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-05-04T12:54:46.707Z"}}}, "cveMetadata": {"cveId": "CVE-2024-26804", "state": "PUBLISHED", "dateUpdated": "2025-05-04T12:54:46.707Z", "dateReserved": "2024-02-19T14:20:24.179Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2024-04-04T08:20:31.305Z", "assignerShortName": "Linux"}, "dataVersion": "5.1"}

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IOW, we skb->data gets \"adjusted\" by a huge value.\n\nThe negative value is returned because skb->head and skb->data distance is\nmore than 64k and skb->network_header (u16) has wrapped around.\n\nThe bug is in the ip_tunnel infrastructure, which can cause\ndev->needed_headroom to increment ad infinitum.\n\nThe syzkaller reproducer consists of packets getting routed via a gre\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\ntunnel.  The ipip encapsulation finds gre0 as next output device.\n\nThis results in the following pattern:\n\n1). First packet is to be sent out via gre0.\nRoute lookup found an output device, ipip0.\n\n2).\nip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the future\noutput device, rt.dev->needed_headroom (ipip0).\n\n3).\nip output / start_xmit moves skb on to ipip0. which runs the same\ncode path again (xmit recursion).\n\n4).\nRouting step for the post-gre0-encap packet finds gre0 as output device\nto use for ipip0 encapsulated packet.\n\ntunl0->needed_headroom is then incremented based on the (already bumped)\ngre0 device headroom.\n\nThis repeats for every future packet:\n\ngre0->needed_headroom gets inflated because previous packets' ipip0 step\nincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0\nneeded_headroom was increased.\n\nFor each subsequent packet, gre/ipip0->needed_headroom grows until\npost-expand-head reallocations result in a skb->head/data distance of\nmore than 64k.\n\nOnce that happens, skb->network_header (u16) wraps around when\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\nafter the headroom expansion/reallocation.\n\nAfter this skb_network_offset(skb) returns a different (and negative)\nresult post headroom expansion.\n\nThe next trip to neigh layer (or anything else that would __skb_pull the\nnetwork header) makes skb->data point to a memory location outside\nskb->head area.\n\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\nprevent perpetual increase instead of dropping the headroom increment\ncompletely."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: ip_tunnel: evita el crecimiento perpetuo del espacio libre syzkaller activado despu\u00e9s de kasan splat: ERROR: KASAN: use-after-free en __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 Lectura del tama\u00f1o 1 en la direcci\u00f3n ffff88812fb4000e mediante la tarea syz-executor183/5191 [..] kasan_report+0xda/0x110 mm/kasan/report.c:588 __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 skb_flow_dissect_flow_key incluir/linux /skbuff.h:1514 [en l\u00ednea] ___skb_get_hash net/core/flow_dissector.c:1791 [en l\u00ednea] __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856 skb_get_hash include/linux/skbuff.h:1556 [en l\u00ednea] ip_tunnel_xmit +0x1855/0x33c0 net/ipv4/ip_tunnel.c:748 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308 __netdev_start_xmit include/linux/netdevice.h:4940 [en l\u00ednea] netdev_start_xmit include/linux/netdevice.h:4954 [en l\u00ednea] xmit_one net/core/dev.c:3548 [en l\u00ednea] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349 dev_queue_xmit include/linux/netdevice .h:3134 [en l\u00ednea] neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592 ... ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235 ip_finish_output+0x31/0x310 net/ipv4/ip_output.c :323 .. iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831 ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665 __netdev_start_xmit incluir /linux /netdevice.h:4940 [en l\u00ednea] netdev_start_xmit include/linux/netdevice.h:4954 [en l\u00ednea] xmit_one net/core/dev.c:3548 [en l\u00ednea] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 . .. El s\u00edmbolo se produce porque skb->data apunta m\u00e1s all\u00e1 del \u00e1rea asignada de skb->head. Esto se debe a que la capa vecina hace: __skb_pull(skb, skb_network_offset(skb)); ... pero skb_network_offset() devuelve un desplazamiento negativo y el argumento __skb_pull() no est\u00e1 firmado. OIA, nosotros, skb->los datos, se \"ajustan\" en un valor enorme. El valor negativo se devuelve porque la distancia de skb->head y skb->data es superior a 64k y skb->network_header (u16) se ha ajustado. El error est\u00e1 en la infraestructura ip_tunnel, lo que puede hacer que dev->needed_headroom se incremente hasta el infinito. El reproductor syzkaller consta de paquetes que se enrutan a trav\u00e9s de un t\u00fanel gre y una ruta de paquetes encapsulados gre que apuntan a otro t\u00fanel (ipip). La encapsulaci\u00f3n ipip encuentra gre0 como el siguiente dispositivo de salida. Esto da como resultado el siguiente patr\u00f3n: 1). El primer paquete se enviar\u00e1 a trav\u00e9s de gre0. La b\u00fasqueda de ruta encontr\u00f3 un dispositivo de salida, ipip0. 2). ip_tunnel_xmit para gre0 aumenta gre0->needed_headroom seg\u00fan el dispositivo de salida futuro, rt.dev->needed_headroom (ipip0). 3). ipoutput/start_xmit mueve skb a ipip0. que ejecuta la misma ruta de c\u00f3digo nuevamente (xmit recursividad). 4). El paso de enrutamiento para el paquete post-gre0-encap encuentra gre0 como dispositivo de salida para usar con el paquete encapsulado ipip0. tunl0->needed_headroom luego se incrementa seg\u00fan el espacio libre del dispositivo gre0 (ya aumentado). Esto se repite para cada paquete futuro: gre0->needed_headroom se infla porque el paso ipip0 de los paquetes anteriores increment\u00f3 el espacio libre rt->dev (gre0), y ipip0 se increment\u00f3 porque se aument\u00f3 el espacio necesario_headroom de gre0. Para cada paquete posterior, gre/ipip0->needed_headroom crece hasta que las reasignaciones posteriores a la expansi\u00f3n del cabezal dan como resultado una distancia skb->head/data de m\u00e1s de 64k. Una vez que eso sucede, skb->network_header (u16) se ajusta cuando pskb_expand_head intenta asegurarse de que skb_network_offset() no cambie despu\u00e9s de la expansi\u00f3n/reasignaci\u00f3n del espacio libre. Despu\u00e9s de esto, skb_network_offset(skb) devuelve un resultado diferente (y negativo) posterior a la expansi\u00f3n del espacio libre.---trucado---"}], "id": "CVE-2024-26804", "lastModified": "2025-03-21T14:58:15.363", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}, "published": "2024-04-04T09:15:09.217", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"affected_release": [{"advisory": "RHSA-2024:4352", "cpe": "cpe:/a:redhat:enterprise_linux:8::nfv", "package": "kernel-rt-0:4.18.0-553.8.1.rt7.349.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-07-08T00:00:00Z"}, {"advisory": "RHSA-2024:4211", "cpe": "cpe:/o:redhat:enterprise_linux:8", "package": "kernel-0:4.18.0-553.8.1.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-07-02T00:00:00Z"}, {"advisory": "RHSA-2024:4447", "cpe": "cpe:/o:redhat:rhel_aus:8.6", "package": "kernel-0:4.18.0-372.111.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support", "release_date": "2024-07-10T00:00:00Z"}, {"advisory": "RHSA-2024:4447", "cpe": "cpe:/o:redhat:rhel_tus:8.6", "package": "kernel-0:4.18.0-372.111.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Telecommunications Update Service", "release_date": "2024-07-10T00:00:00Z"}, {"advisory": "RHSA-2024:4447", "cpe": "cpe:/o:redhat:rhel_e4s:8.6", "package": "kernel-0:4.18.0-372.111.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions", "release_date": "2024-07-10T00:00:00Z"}, {"advisory": "RHSA-2024:4740", "cpe": "cpe:/o:redhat:rhel_eus:8.8", "package": "kernel-0:4.18.0-477.64.1.el8_8", "product_name": "Red Hat Enterprise Linux 8.8 Extended Update Support", "release_date": "2024-07-23T00:00:00Z"}, {"advisory": "RHSA-2024:3306", "cpe": "cpe:/a:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-427.18.1.el9_4", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2024-05-23T00:00:00Z"}, {"advisory": "RHSA-2024:3306", "cpe": "cpe:/o:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-427.18.1.el9_4", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2024-05-23T00:00:00Z"}, {"advisory": "RHSA-2024:3461", "cpe": "cpe:/a:redhat:rhel_eus:9.2", "package": "kernel-0:5.14.0-284.67.1.el9_2", "product_name": "Red Hat Enterprise Linux 9.2 Extended Update Support", "release_date": "2024-05-29T00:00:00Z"}, {"advisory": "RHSA-2024:3460", "cpe": "cpe:/a:redhat:rhel_eus:9.2::nfv", "package": "kernel-rt-0:5.14.0-284.67.1.rt14.352.el9_2", "product_name": "Red Hat Enterprise Linux 9.2 Extended Update Support", "release_date": "2024-05-29T00:00:00Z"}], "bugzilla": {"description": "kernel: net: ip_tunnel: prevent perpetual headroom growth", "id": "2273423", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2273423"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "verified"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nnet: ip_tunnel: prevent perpetual headroom growth\nsyzkaller triggered following kasan splat:\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\n[..]\nkasan_report+0xda/0x110 mm/kasan/report.c:588\n__skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\nskb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\n___skb_get_hash net/core/flow_dissector.c:1791 [inline]\n__skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\nskb_get_hash include/linux/skbuff.h:1556 [inline]\nip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\nipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\n__netdev_start_xmit include/linux/netdevice.h:4940 [inline]\nnetdev_start_xmit include/linux/netdevice.h:4954 [inline]\nxmit_one net/core/dev.c:3548 [inline]\ndev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n__dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\ndev_queue_xmit include/linux/netdevice.h:3134 [inline]\nneigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\n...\nip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\nip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\n..\niptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\nip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\nipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\n__netdev_start_xmit include/linux/netdevice.h:4940 [inline]\nnetdev_start_xmit include/linux/netdevice.h:4954 [inline]\nxmit_one net/core/dev.c:3548 [inline]\ndev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n...\nThe splat occurs because skb->data points past skb->head allocated area.\nThis is because neigh layer does:\n__skb_pull(skb, skb_network_offset(skb));\n... but skb_network_offset() returns a negative offset and __skb_pull()\narg is unsigned.  IOW, we skb->data gets \"adjusted\" by a huge value.\nThe negative value is returned because skb->head and skb->data distance is\nmore than 64k and skb->network_header (u16) has wrapped around.\nThe bug is in the ip_tunnel infrastructure, which can cause\ndev->needed_headroom to increment ad infinitum.\nThe syzkaller reproducer consists of packets getting routed via a gre\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\ntunnel.  The ipip encapsulation finds gre0 as next output device.\nThis results in the following pattern:\n1). First packet is to be sent out via gre0.\nRoute lookup found an output device, ipip0.\n2).\nip_tunnel_xmit for gre0 bumps gre0->needed_headroom based on the future\noutput device, rt.dev->needed_headroom (ipip0).\n3).\nip output / start_xmit moves skb on to ipip0. which runs the same\ncode path again (xmit recursion).\n4).\nRouting step for the post-gre0-encap packet finds gre0 as output device\nto use for ipip0 encapsulated packet.\ntunl0->needed_headroom is then incremented based on the (already bumped)\ngre0 device headroom.\nThis repeats for every future packet:\ngre0->needed_headroom gets inflated because previous packets' ipip0 step\nincremented rt->dev (gre0) headroom, and ipip0 incremented because gre0\nneeded_headroom was increased.\nFor each subsequent packet, gre/ipip0->needed_headroom grows until\npost-expand-head reallocations result in a skb->head/data distance of\nmore than 64k.\nOnce that happens, skb->network_header (u16) wraps around when\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\nafter the headroom expansion/reallocation.\nAfter this skb_network_offset(skb) returns a different (and negative)\nresult post headroom expansion.\nThe next trip to neigh layer (or anything else that would __skb_pull the\nnetwork header) makes skb->data point to a memory location outside\nskb->head area.\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\nprevent perpetual increase instead of dropping the headroom increment\ncompletely.", "A use-after-free flaw was found in the Linux kernel\u2019s ip_tunnel functionality when a user uses the ip_tunnel infrastructure. This flaw allows a\u00a0local user to crash the system."], "name": "CVE-2024-26804", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-04-04T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2024-26804\nhttps://nvd.nist.gov/vuln/detail/CVE-2024-26804\nhttps://lore.kernel.org/linux-cve-announce/2024040404-CVE-2024-26804-a6ff@gregkh/T"], "threat_severity": "Moderate"}