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CVE-2026-23240 Linux CVE debrief

CVE-2026-23240 is a critical Linux kernel race condition in the TLS work-cancellation path. The bug can allow tx_work_handler() to be scheduled again after close-time cancellation, creating a use-after-free risk against freed TLS state.

Vendor
Linux
Product
Unknown
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-10
Original CVE updated
2026-05-20
Advisory published
2026-03-10
Advisory updated
2026-05-20

Who should care

Linux kernel maintainers, distro security teams, and operators running affected Linux kernel releases—especially systems that use the kernel TLS networking path.

Technical summary

According to the CVE description, tls_sw_cancel_work_tx() calls cancel_delayed_work_sync() from tls_sk_proto_close(), but tx_work_handler() can still be scheduled again from paths such as the Delayed ACK handler or ksoftirqd. That race can let the worker dereference a freed TLS object. The fix replaces cancel_delayed_work_sync() with disable_delayed_work_sync() to prevent the rescheduling window. NVD classifies the weakness as CWE-362 and rates it CVSS 3.1 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Defensive priority

Critical / urgent

Recommended defensive actions

  • Apply the Linux kernel updates that include the stable fixes referenced by kernel.org.
  • Verify whether your fleet is running an affected kernel range listed by NVD and ensure your vendor backport includes the fix.
  • Prioritize hosts that use Linux kernel TLS or related networking paths for validation and patch rollout.
  • Reboot into the patched kernel after installation and confirm the fixed build is active.
  • Monitor distro/security advisories for backported fixes; the supplied corpus does not describe a safe workaround.

Evidence notes

The supplied CVE description states the issue was found during a code audit and explains the race in tls_sw_cancel_work_tx(). NVD marks the record as analyzed, assigns CVSS 9.8, and lists CWE-362. The reference set includes four official kernel.org stable patch links, supporting that the issue was fixed in kernel maintenance branches.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-23240 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-23240

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-23240 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-23240

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/17153f154f80be2b47ebf52840f2d8f724eb2f3b

    416baaa9-dc9f-4396-8d5f-8c081fb06d67 - Patch

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/7bb09315f93dce6acc54bf59e5a95ba7365c2be4

    416baaa9-dc9f-4396-8d5f-8c081fb06d67 - Patch

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/854cd32bc74fe573353095e90958490e4e4d641b

    416baaa9-dc9f-4396-8d5f-8c081fb06d67 - Patch

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/a5de36d6cee74a92c1a21b260bc507e64bc451de

    416baaa9-dc9f-4396-8d5f-8c081fb06d67 - Patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.