CVE entry · CVE-2025-39682
CVE-2025-39682: Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
Linux Kernel contains an improper check for unusual or exceptional conditions vulnerability in the TLS receive path which allows a zero-length record retrieved from the rx_list to bypass the intended recvmsg() record-type handling, potentially causing subsequent TLS records to be processed using incorrect zero-copy and queuing assumptions. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.
- Actively exploited: added to CISA’s KEV catalog on September 18, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: September 21, 2026.
Description from CISA’s KEV catalog.
What to do
- Check whether your estate includes Linux Kernel, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.
References
- Vendor advisory or reference cited by CISA (git.kernel.org)
- Vendor advisory or reference cited by CISA (git.kernel.org)
- Vendor advisory or reference cited by CISA (git.kernel.org)
- Vendor advisory or reference cited by CISA (git.kernel.org)
- Vendor advisory or reference cited by CISA (git.kernel.org)
- NVD entry (NIST)
- CISA KEV catalog