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CVE-2025-39682: Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
CVE-2025-39682: critical vulnerability affecting Kernel. Check CVSS, KEV status, business impact and recommended administrator actions.
- CVSS
- 9.8 CRITICAL
- EPSS
- 66.36%
- Known exploited
- yes
- Product
- Kernel
What is known
In the Linux kernel, the following vulnerability has been resolved: tls: fix handling of zero-length records on the rx_list Each recvmsg() call must process either - only contiguous DATA records (any number of them) - one non-DATA record If the next record has different type than what has already been processed we break out of the main processing loop. If the record has already been decrypted (which may be the case for TLS 1.3 where we don't know type until decryption) we queue the pending record to the rx_list. Next recvmsg() will pick it up from there. Queuing the skb to rx_list after zero-copy decrypt is not possible, since in that case we decrypted directly to the user space buffer, and we don't have an skb to queue (darg.skb points to the ciphertext skb for access to metadata like length). Only data records are allowed zero-copy, and we break the processing loop after each non-data record. So we should never zero-copy and then find out that the record type has changed. The corner case we missed is when the initial record comes from rx_list, and it's zero length.
Business impact
Successful exploitation of CVE-2025-39682, a critical vulnerability (CVSS 9.8) affecting Kernel, may affect the confidentiality, integrity or availability of the vulnerable environment. The exact impact depends on the installed version, exposed interfaces and deployment configuration. CISA lists this vulnerability in the Known Exploited Vulnerabilities catalog, so exposed systems should be treated as a priority.
Recommended administrator action
Confirm whether Kernel is present and compare installed versions with the vendor advisory and NVD record. Apply the vendor patch or documented mitigation; until remediation is complete, reduce exposure of affected interfaces, review relevant logs and monitor for indicators of exploitation. Where applicable, include the CISA KEV remediation due date of 2026-09-21 in the change plan. DataHouse can support version verification, managed patching, network exposure reduction, log review and backup validation for dedicated, cloud and colocated environments.