CVE-2025-39682, a CVSS 9.8-rated flaw in the Linux kernel TLS receive path, has been added to CISA's Known Exploited Vulnerabilities (KEV) catalogue following confirmed evidence of active exploitation in the wild. The vulnerability arises from an improper check for unusual or exceptional conditions in the kernel's TLS processing logic, a class of flaw that has historically enabled privilege escalation and remote code execution in susceptible environments.
CISA's addition to the KEV catalogue on 18 September 2026 triggers mandatory remediation timelines for Federal Civilian Executive Branch (FCEB) agencies under Binding Operational Directive (BOD) 26-04. CISA explicitly characterised this vulnerability type as a frequent attack vector for malicious cyber actors, citing significant risk to the federal enterprise. The urgency of federal guidance signals that exploitation is unlikely to remain confined to government-adjacent targets.
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