{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-41319", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-04-20T14:01:46.671Z", "datePublished": "2026-04-24T03:07:24.335Z", "dateUpdated": "2026-04-25T01:46:35.002Z"}, "containers": {"cna": {"title": "MailKit has STARTTLS Response Injection via unflushed stream buffer that enables SASL mechanism downgrade", "problemTypes": [{"descriptions": [{"cweId": "CWE-74", "lang": "en", "description": "CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr"}], "affected": [{"vendor": "jstedfast", "product": "MailKit", "versions": [{"version": "< 4.16.0", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-04-24T03:07:24.335Z"}, "descriptions": [{"lang": "en", "value": "MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext-to-TLS trust boundary, enabling SASL authentication mechanism downgrade (e.g., forcing PLAIN instead of SCRAM-SHA-256). The internal read buffer in `SmtpStream`, `ImapStream`, and `Pop3Stream` is not flushed when the underlying stream is replaced with `SslStream` during STARTTLS upgrade, causing pre-TLS attacker-injected data to be processed as trusted post-TLS responses. Version 4.16.0 patches the issue."}], "source": {"advisory": "GHSA-9j88-vvj5-vhgr", "discovery": "UNKNOWN"}}, "adp": [{"references": [{"url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr", "tags": ["exploit"]}], "metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-25T01:46:14.462850Z", "id": "CVE-2026-41319", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-25T01:46:35.002Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-41319", "role": "CISA Coordinator", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-04-25T01:46:14.462850Z"}}}], "references": [{"url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr", "tags": ["exploit"]}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-25T01:46:30.490Z"}}], "cna": {"title": "MailKit has STARTTLS Response Injection via unflushed stream buffer that enables SASL mechanism downgrade", "source": {"advisory": "GHSA-9j88-vvj5-vhgr", "discovery": "UNKNOWN"}, "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}}], "affected": [{"vendor": "jstedfast", "product": "MailKit", "versions": [{"status": "affected", "version": "< 4.16.0"}]}], "references": [{"url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr", "name": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr", "tags": ["x_refsource_CONFIRM"]}], "descriptions": [{"lang": "en", "value": "MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext-to-TLS trust boundary, enabling SASL authentication mechanism downgrade (e.g., forcing PLAIN instead of SCRAM-SHA-256). The internal read buffer in `SmtpStream`, `ImapStream`, and `Pop3Stream` is not flushed when the underlying stream is replaced with `SslStream` during STARTTLS upgrade, causing pre-TLS attacker-injected data to be processed as trusted post-TLS responses. Version 4.16.0 patches the issue."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-74", "description": "CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-04-24T03:07:24.335Z"}}}, "cveMetadata": {"cveId": "CVE-2026-41319", "state": "PUBLISHED", "dateUpdated": "2026-04-25T01:46:35.002Z", "dateReserved": "2026-04-20T14:01:46.671Z", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "datePublished": "2026-04-24T03:07:24.335Z", "assignerShortName": "GitHub_M"}, "dataVersion": "5.2"}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext-to-TLS trust boundary, enabling SASL authentication mechanism downgrade (e.g., forcing PLAIN instead of SCRAM-SHA-256). The internal read buffer in `SmtpStream`, `ImapStream`, and `Pop3Stream` is not flushed when the underlying stream is replaced with `SslStream` during STARTTLS upgrade, causing pre-TLS attacker-injected data to be processed as trusted post-TLS responses. Version 4.16.0 patches the issue."}], "id": "CVE-2026-41319", "lastModified": "2026-04-25T03:16:04.600", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "[email protected]", "type": "Secondary"}]}, "published": "2026-04-24T04:16:20.400", "references": [{"source": "[email protected]", "url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr"}], "sourceIdentifier": "[email protected]", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-74"}], "source": "[email protected]", "type": "Secondary"}]}

{}