{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74696", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.926Z", "datePublished": "2026-08-22T15:32:58.414Z", "dateUpdated": "2026-10-16T19:16:09.811Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-25T05:41:40.079Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix TFO max_qlen accounting across reuseport migration\n\nA listener's TCP_FASTOPEN max_qlen stops being accurate and lets through\nfar more pending Fast Open requests than it was configured for.\n\nThis only shows up with SO_REUSEPORT listener migration, where closing a\nlistener hands its still-pending TFO children over to a surviving one.\n\nfastopenq.qlen is charged in tcp_fastopen_create_child() when the child\nis created and uncharged in reqsk_fastopen_remove() when the handshake\ncompletes. The uncharge follows rsk_listener of the request the child\npoints at, and inet_reqsk_clone() has repointed the child at a new\nrequest owned by the new listener, so the ++ and the -- land on two\ndifferent sockets. The new listener's qlen drifts negative and its\nlimit no longer binds.\n\nCharge the new listener during migration, like reqsk_queue_migrated()\nalready does for queue->young and queue->qlen." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The bug is in the inbound TCP SYN/TFO server path (tcp_v4_rcv/tcp_conn_request/tcp_try_fastopen), reachable by sending TCP Fast Open SYN packets to any internet-facing listener with server-side TFO enabled.\nAC:L - An attacker fully controls the TFO SYN flood; once a SO_REUSEPORT worker closes while TFO children are pending (routine nginx/k8s reloads), migration deterministically skews qlen negative with no narrow race or special memory layout required.\nPR:N - Exploitation needs only unauthenticated network reachability to the listening TCP port; no target credentials, capabilities, or local access are required because TFO SYN processing occurs before any application authentication.\nUI:N - No victim user action is needed beyond normal server operation; the remote attacker sends crafted TFO SYN traffic and benefits automatically when reuseport listener migration occurs during ordinary worker shutdown or reload.\nS:U - Impact is confined to the target host kernel TCP stack resource limits and availability; it does not cross VM, container, or IOMMU security boundaries to affect a different authority.\nC:N - The flaw is a signed counter accounting mismatch on fastopenq.qlen; it does not corrupt memory, leak kernel pointers, or provide an out-of-bounds read or use-after-free disclosure primitive.\nI:N - No arbitrary memory write, control-flow hijack, or unauthorized persistent data modification occurs; bypassing max_qlen only relaxes a rate limit while TFO cookie validation and normal TCP semantics still govern accepted data.\nA:H - With max_qlen disabled, a remote attacker can create far more pending TFO child sockets and SYN-carrying skbs than configured, exhausting kernel memory and socket tables and causing severe denial of service or OOM-induced host instability." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/inet_connection_sock.c" ], "versions": [ { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "e98f0d80b9cccb5f828425d2004f9686e7d1ae24", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "b6247e0f96bd825ffb2005257f6177b5e642dee6", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "585fc5247d14939a561056aa2addd9b7c2b1f670", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "6e10ee56524a26b250229ad348637825646ddb88", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "a66e869cf0c90c1e47ae75f72b6482acbfc808ff", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "d974618b2097453778389d385e3741629c40e0a3", "status": "affected", "versionType": "git" }, { "version": "54b92e84193749c9968aff2dd46e3b0f42643e18", "lessThan": "a0ab2ba83e35159d81cec830a92e885ecf8139be", "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/inet_connection_sock.c" ], "versions": [ { "version": "5.14", "status": "affected" }, { "version": "0", "lessThan": "5.14", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.216", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.183", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.152", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.104", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.45", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.9", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "5.14", "versionEndExcluding": "5.15.216" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.1.183" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.6.152" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.12.104" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "6.18.45" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.1.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.14", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24" }, { "url": "https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6" }, { "url": "https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670" }, { "url": "https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88" }, { "url": "https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff" }, { "url": "https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3" }, { "url": "https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be" } ], "title": "tcp: fix TFO max_qlen accounting across reuseport migration", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-74696", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:14:45.391260Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:16:09.811Z" } } ] } }