{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-43121", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-05-01T14:12:55.987Z", "datePublished": "2026-05-06T11:27:08.216Z", "dateUpdated": "2026-05-06T11:27:08.216Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-06T11:27:08.216Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/zcrx: fix user_ref race between scrub and refill paths\n\nThe io_zcrx_put_niov_uref() function uses a non-atomic\ncheck-then-decrement pattern (atomic_read followed by separate\natomic_dec) to manipulate user_refs. This is serialized against other\ncallers by rq_lock, but io_zcrx_scrub() modifies the same counter with\natomic_xchg() WITHOUT holding rq_lock.\n\nOn SMP systems, the following race exists:\n\n CPU0 (refill, holds rq_lock) CPU1 (scrub, no rq_lock)\n put_niov_uref:\n atomic_read(uref) - 1\n // window opens\n atomic_xchg(uref, 0) - 1\n return_niov_freelist(niov) [PUSH #1]\n // window closes\n atomic_dec(uref) - wraps to -1\n returns true\n return_niov(niov)\n return_niov_freelist(niov) [PUSH #2: DOUBLE-FREE]\n\nThe same niov is pushed to the freelist twice, causing free_count to\nexceed nr_iovs. Subsequent freelist pushes then perform an out-of-bounds\nwrite (a u32 value) past the kvmalloc'd freelist array into the adjacent\nslab object.\n\nFix this by replacing the non-atomic read-then-dec in\nio_zcrx_put_niov_uref() with an atomic_try_cmpxchg loop that atomically\ntests and decrements user_refs. This makes the operation safe against\nconcurrent atomic_xchg from scrub without requiring scrub to acquire\nrq_lock.\n\n[pavel: removed a warning and a comment]"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["io_uring/zcrx.c"], "versions": [{"version": "34a3e60821ab9f335a58d43a88cccdbefdebdec3", "lessThan": "a94f096e28bfc7975163a6b80f1c8f323efe317a", "status": "affected", "versionType": "git"}, {"version": "34a3e60821ab9f335a58d43a88cccdbefdebdec3", "lessThan": "485dc691257b96e6d3bdc25b0eff2daadcc5c46c", "status": "affected", "versionType": "git"}, {"version": "34a3e60821ab9f335a58d43a88cccdbefdebdec3", "lessThan": "003049b1c4fb8aabb93febb7d1e49004f6ad653b", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["io_uring/zcrx.c"], "versions": [{"version": "6.15", "status": "affected"}, {"version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.16", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.6", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0", "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": "6.15", "versionEndExcluding": "6.18.16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "6.19.6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.0"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/a94f096e28bfc7975163a6b80f1c8f323efe317a"}, {"url": "https://git.kernel.org/stable/c/485dc691257b96e6d3bdc25b0eff2daadcc5c46c"}, {"url": "https://git.kernel.org/stable/c/003049b1c4fb8aabb93febb7d1e49004f6ad653b"}], "title": "io_uring/zcrx: fix user_ref race between scrub and refill paths", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/zcrx: fix user_ref race between scrub and refill paths\n\nThe io_zcrx_put_niov_uref() function uses a non-atomic\ncheck-then-decrement pattern (atomic_read followed by separate\natomic_dec) to manipulate user_refs. This is serialized against other\ncallers by rq_lock, but io_zcrx_scrub() modifies the same counter with\natomic_xchg() WITHOUT holding rq_lock.\n\nOn SMP systems, the following race exists:\n\n CPU0 (refill, holds rq_lock) CPU1 (scrub, no rq_lock)\n put_niov_uref:\n atomic_read(uref) - 1\n // window opens\n atomic_xchg(uref, 0) - 1\n return_niov_freelist(niov) [PUSH #1]\n // window closes\n atomic_dec(uref) - wraps to -1\n returns true\n return_niov(niov)\n return_niov_freelist(niov) [PUSH #2: DOUBLE-FREE]\n\nThe same niov is pushed to the freelist twice, causing free_count to\nexceed nr_iovs. Subsequent freelist pushes then perform an out-of-bounds\nwrite (a u32 value) past the kvmalloc'd freelist array into the adjacent\nslab object.\n\nFix this by replacing the non-atomic read-then-dec in\nio_zcrx_put_niov_uref() with an atomic_try_cmpxchg loop that atomically\ntests and decrements user_refs. This makes the operation safe against\nconcurrent atomic_xchg from scrub without requiring scrub to acquire\nrq_lock.\n\n[pavel: removed a warning and a comment]"}], "id": "CVE-2026-43121", "lastModified": "2026-05-06T13:07:51.607", "metrics": {}, "published": "2026-05-06T12:16:28.950", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/003049b1c4fb8aabb93febb7d1e49004f6ad653b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/485dc691257b96e6d3bdc25b0eff2daadcc5c46c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a94f096e28bfc7975163a6b80f1c8f323efe317a"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"bugzilla": {"description": "kernel: io_uring/zcrx: fix user_ref race between scrub and refill paths", "id": "2467110", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2467110"}, "csaw": false, "cwe": "CWE-366", "details": ["A flaw was found in the `io_uring/zcrx` component of the Linux kernel. This vulnerability involves a race condition where two operations can manipulate the same memory counter simultaneously without proper synchronization. This can lead to a memory object being freed twice, followed by an out-of-bounds write. Such memory corruption could allow a local attacker to escalate privileges or execute arbitrary code, potentially compromising the system."], "name": "CVE-2026-43121", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-05-06T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-43121\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-43121\nhttps://lore.kernel.org/linux-cve-announce/2026050618-CVE-2026-43121-2a26@gregkh/T"]}