CVE-2025-39682: in the CISA KEV catalogue
Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability. CISA added CVE-2025-39682 to the Known Exploited Vulnerabilities catalogue on 2026-09-18 with a default due date of 2026-09-21. Known ransomware campaign use: Unknown. Forensic triage flag: Yes.
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. (CISA description)
- Vendor / product
- Linux Kernel
- CWE
- CWE-754
- CISA 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.
- EPSS
- 3.3%, percentile 88 (scored 2026-11-03)
EPSS puts about 3.3 in 100 odds (3.3%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 88% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
- https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
- https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
- https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
- https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
- https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2025-39682 in the CISA KEV catalogue?
Yes. CISA added CVE-2025-39682 (Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-09-18. CISA's default due date for it is 2026-09-21.
Is CVE-2025-39682 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2025-39682. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2025-39682?
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.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2025-39682