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CVE-2026-74696

tcp: fix TFO max_qlen accounting across reuseport migration

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

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.

Timeline

  1. CVE published55 days
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux 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 Linux

    5.14

  • KernelLinux

    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

References 7

git.kernel.org