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.

VendorLinux
ProductKernel
Date added to KEV2026-09-18
Due date (BOD 22-01)2026-09-21
Known ransomware campaign useUnknown
CWECWE-754
Required actionApply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

What to do

  1. Identify every instance of Linux Kernel in your environment (asset inventory, EDR, vulnerability scanner).
  2. Apply CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
  3. Federal civilian agencies must act by 2026-09-21 under BOD 22-01; other organizations can use the same date as a target.
  4. Check the vendor advisory and NVD entry linked below for affected versions, then record the fix in your change log.

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Sources

Generated from the CISA feed with AI assistance; facts are taken verbatim from the feed. Not affiliated with or endorsed by CISA. Facts come from the CISA Known Exploited Vulnerabilities catalog (public domain).