CVE intelligenceCISA KEV

CVE-2025-39682

Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability

Published Sep 5, 2025Sources checked Oct 3, 2026

9.8CRITICALCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2025-39682 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Linux Kernel.

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.

CISA KEVListedObserved exploitation

EPSS2.9%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors1Source-linked actor relationships

Overview

What is CVE-2025-39682?

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.