CVE-2026-74696 (GCVE-0-2026-74696)
Vulnerability from cvelistv5
Published
2026-08-22 15:32
Modified
2026-08-25 05:41
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
tcp: fix TFO max_qlen accounting across reuseport migration
A listener's TCP_FASTOPEN max_qlen stops being accurate and lets through
far more pending Fast Open requests than it was configured for.
This only shows up with SO_REUSEPORT listener migration, where closing a
listener hands its still-pending TFO children over to a surviving one.
fastopenq.qlen is charged in tcp_fastopen_create_child() when the child
is created and uncharged in reqsk_fastopen_remove() when the handshake
completes. The uncharge follows rsk_listener of the request the child
points at, and inet_reqsk_clone() has repointed the child at a new
request owned by the new listener, so the ++ and the -- land on two
different sockets. The new listener's qlen drifts negative and its
limit no longer binds.
Charge the new listener during migration, like reqsk_queue_migrated()
already does for queue->young and queue->qlen.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 Version: 54b92e84193749c9968aff2dd46e3b0f42643e18 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv4/inet_connection_sock.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "e98f0d80b9cccb5f828425d2004f9686e7d1ae24",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "b6247e0f96bd825ffb2005257f6177b5e642dee6",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "585fc5247d14939a561056aa2addd9b7c2b1f670",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "6e10ee56524a26b250229ad348637825646ddb88",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "a66e869cf0c90c1e47ae75f72b6482acbfc808ff",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "d974618b2097453778389d385e3741629c40e0a3",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
},
{
"lessThan": "a0ab2ba83e35159d81cec830a92e885ecf8139be",
"status": "affected",
"version": "54b92e84193749c9968aff2dd46e3b0f42643e18",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/ipv4/inet_connection_sock.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.14"
},
{
"lessThan": "5.14",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.152",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.104",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.45",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.216",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.183",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.152",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.104",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.45",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.9",
"versionStartIncluding": "5.14",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "5.14",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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\u0027s 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\u0027s qlen drifts negative and its\nlimit no longer binds.\n\nCharge the new listener during migration, like reqsk_queue_migrated()\nalready does for queue-\u003eyoung and queue-\u003eqlen."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-25T05:41:40.079Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74696",
"datePublished": "2026-08-22T15:32:58.414Z",
"dateReserved": "2026-08-15T05:44:03.926Z",
"dateUpdated": "2026-08-25T05:41:40.079Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…