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VulnerabilityPublished Updated

CVE-2026-23240: Linux kernel · tls: Fix race condition in tls_sw_cancel_work_tx()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in a5de36d6cee74a92c1a21b260bc507e64bc451de : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:18 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in a5de36d6cee74a92c1a21b260bc507e64bc451de, 17153f154f80be2b47ebf52840f2d8f724eb2f3b, 854cd32bc74fe573353095e90958490e4e4d641b +1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Mar 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 Linux kernel to a5de36d6cee74a92c1a21b260bc507e64bc451de, 17153f154f80be2b47ebf52840f2d8f724eb2f3b, 854cd32bc74fe573353095e90958490e4e4d641b or 7bb09315f93dce6acc54bf59e5a95ba7365c2be4.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ f87e62d45e51b12d48d2cb46b5cde8f83b866bc4, < a5de36d6cee74a92c1a21b260bc507e64bc451de
Fixed in
  • a5de36d6cee74a92c1a21b260bc507e64bc451de
LinuxLinuxAffected
  • ≥ f87e62d45e51b12d48d2cb46b5cde8f83b866bc4, < 17153f154f80be2b47ebf52840f2d8f724eb2f3b
Fixed in
  • 17153f154f80be2b47ebf52840f2d8f724eb2f3b
LinuxLinuxAffected
  • ≥ f87e62d45e51b12d48d2cb46b5cde8f83b866bc4, < 854cd32bc74fe573353095e90958490e4e4d641b
Fixed in
  • 854cd32bc74fe573353095e90958490e4e4d641b
LinuxLinuxAffected
  • ≥ f87e62d45e51b12d48d2cb46b5cde8f83b866bc4, < 7bb09315f93dce6acc54bf59e5a95ba7365c2be4
Fixed in
  • 7bb09315f93dce6acc54bf59e5a95ba7365c2be4
LinuxLinuxAffected
  • =5.3
Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel source code as indicated by the fixed commit versions. Users and administrators should update their Linux kernel to a version that includes these fixes to remediate the vulnerability. No alternative mitigations are indicated by the vendor advisory.

Description

CVE-2026-23240 is a critical race condition vulnerability in the Linux kernel's TLS implementation. The issue occurs in the tls_sw_cancel_work_tx() function where a delayed work handler (tx_work_handler) may be scheduled after the TLS object it references has been freed, leading to a use-after-free scenario. This race condition arises because cancel_delayed_work_sync() does not fully prevent the tx_work_handler from being scheduled concurrently from other kernel contexts. The flaw was discovered during a code audit and fixed by replacing cancel_delayed_work_sync() with disable_delayed_work_sync() to properly prevent the race.

References

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