Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Linux, fix it now.
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.
US federal civilian agencies must remediate by Sep 21, 2026.
Official fix available since
Apply the vendor's update to every affected system. Check the fixed-in versions below where known.
Basis: NVD patch reference
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.
Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.
| Product | Vendor | Affected versions | Fixed in | Source |
|---|---|---|---|---|
| Linux | Linux | >= 6.0, < 6.1.149; >= 6.2, < 6.6.103; >= 6.7, < 6.12.44; >= 6.13, < 6.16.4; 6.17 | 6.1.149; 6.6.103; 6.12.44; 6.16.4 | KEV |
Sources: KEV = CISA Known Exploited Vulnerabilities catalog.
Developments from the last 30 days, newest first.
CVE-2025-39682 scored CVSS 9.8: Linux Kernel, Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
CISA lists this as exploited in the wild. Unpatched Kernel systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
Patch released for CVE-2025-39682: Linux Kernel, Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
An official fix is now available for Linux Kernel. This vulnerability is being exploited, so apply it promptly.
Basis: NVD patch reference
CVE-2025-39682 added to CISA KEV: Linux Kernel, Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
CISA lists this as exploited in the wild. Unpatched Kernel systems are exposed to active attacks now.
Basis: CISA Known Exploited Vulnerabilities catalog
CISA lists this as exploited in the wild. Unpatched Linux systems are exposed to active attacks now.
Treat this as an emergency.
