CISA KEV Flags Linux Kernel TLS Receive Path Flaw CVE-2025-39682

En bref

• CISA KEV lists a Linux kernel TLS receive-path vulnerability tracked as CVE-2025-39682.
• A zero-length record from rx_list can bypass intended recvmsg() record-type handling.
• Later TLS records may be processed with incorrect zero-copy and queuing assumptions.
• Some affected products may be end-of-life or end-of-service; migrate to supported versions.
• Apply vendor mitigations and follow CISA BOD 26-04 and forensics triage guidance.

CISA's Known Exploited Vulnerabilities catalog includes a Linux kernel issue affecting the TLS receive path, tracked as CVE-2025-39682. The flaw involves an improper check for unusual or exceptional conditions. A zero-length record retrieved from the rx_list can bypass the intended recvmsg() record-type handling, which may cause later TLS records to be processed using incorrect zero-copy and queuing assumptions.

This matters for any Linux-based system that relies on kernel TLS. In K-12 environments, that can include servers, virtualisation hosts, network appliances, web filters, VPN gateways, and storage systems. Districts may not always know whether a vendor appliance uses kernel TLS internally, so vendor advisories and product inventories are important. The CISA KEV listing signals that this is a known exploited vulnerability and should be treated as a priority rather than a routine kernel bug.

The excerpt also warns that impacted products could be end-of-life or end-of-service. If a device or platform cannot receive a supported kernel or firmware update, continuing to run it increases risk. CISA's required action points to vendor mitigations, BOD 26-04 risk-based prioritisation, and forensics triage requirements. Those requirements are aimed at federal agencies, but they are a useful baseline for school districts and other public-sector teams.

What to watch: confirm whether your Linux kernels or vendor products are affected by CVE-2025-39682. Check for patches, updated firmware, or documented mitigations. If no fix exists, consider disabling kernel TLS where feasible, isolating the system, or replacing unsupported equipment. Monitor for TLS anomalies, crashes, or unexpected record handling that could indicate exploitation attempts.

Because details such as exact affected kernel versions, exploit conditions, and vendor-specific impact are not fully provided here, verify them against NVD, CISA, and your vendors before making changes. Do not assume that a single patch covers every Linux-based appliance in the environment.

À faire maintenant

1. Inventory all Linux-based servers, appliances, VPNs, proxies, and virtualisation hosts, and identify where kernel TLS is enabled or used.
2. Check vendor advisories and NVD for CVE-2025-39682, then apply kernel, firmware, or product updates as soon as supported versions are available.
3. If no patch exists, apply vendor mitigations or disable kernel TLS on affected systems where operationally feasible.
4. Replace or isolate end-of-life and end-of-service products that cannot be patched or mitigated.
5. Follow CISA BOD 26-04 prioritisation and forensics triage guidance for internet-facing or high-value assets.
6. Restrict internet exposure of affected systems until remediation is complete, and review logs for TLS-related anomalies or crashes.
7. Document affected assets, patch status, and compensating controls for incident response and compliance reporting.

Source originale

CISA Known Exploited Vulnerabilities