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VulnerabilityPublished Updated

CVE-2026-74692: Linux kernel · net/smc: fix TOCTOU race between smc_listen_out() and listener close

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · CVSS 7.5 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.

Data as of 28 Oct 2026, 01:00 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +28
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threatsAffected
  • 6.17.0-5.5 – 7.0.0-38.38
23 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threatsAffected
  • 6.17.0-1002.2 – 7.0.0-1014.14
15 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threatsAffected
  • 6.17.0-1003.3 – 7.0.0-1017.17
15 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threatsAffected
  • 7.0.0-1003.3 – 7.0.0-1016.16
9 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threatsAffected
  • 6.17.0-1002.2 – 7.0.0-1014.14
13 affected builds
Fixed in–
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threatsAffected
  • 7.0.0-1002.3 – 7.0.0-1008.9
6 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix TOCTOU race between smc_listen_out() and listener close smc_listen_out() reads lsmc->sk.sk_state without the listener lock, then acquires lock_sock_nested() only after the check passes. This opens a window where smc_close_active() can transition the listener to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept queue, and release the lock, all between the lockless read and the delayed lock acquisition: smc_listen_work (smc_hs_wq) smc_close_active() ------------------------------- ------------------------- release_sock(child) if (sk_state == SMC_LISTEN) TRUE lock_sock(listener) sk_state = SMC_CLOSED smc_close_cleanup_listen() release_sock(listener) flush_work(tcp_listen_work) lock_sock_nested(listener) smc_accept_enqueue(listener, child) /* child enqueued on dead listener */ smc_close_active() flushes only tcp_listen_work. Work items already dispatched onto smc_hs_wq for the CLC handshake continue running unguarded. smc_accept_enqueue() takes a sock_hold() on the child that is never released, so the child smc_sock, its clcsock, and the reference all leak. A remote peer that opens TCP connections while the server calls close() can exhaust kernel memory. Move lock_sock_nested() to before the sk_state check so that the test and the enqueue are atomic under the listener lock.

References

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