CVE-2025-39682: tls: fix handling of zero-length records on the rx_list

Description

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.

Exploited in the wild

CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability.

Added: 18 Sept 2026
Fix due (US federal): 21 Sept 2026
Used by ransomware: Not known

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.

Scores

CVSS scores of CVE-2025-39682, by who scored it
Scored by	CVSS	Score	Vector
LinuxCNA (assigner)	3.1	Critical9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Analyzed	3.1	Critical9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS (exploitation in 30 days): 3.2% · top 12% of all CVEs (6 Nov 2026)
CISA SSVC: Exploitation: active · Automatable: yes · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.

Weakness

CWE-754 Improper Check for Unusual or Exceptional Conditions (opens in a new tab)All about CWE-754 and its CVEs

Affected products

Linux · Linux
- affected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 – < 2902c3ebcca52ca845c03182000e8d71d3a5196f
- affected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 – < c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
- affected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 – < 3439c15ae91a517cf3c650ea15a8987699416ad9
- affected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 – < 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
- affected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 – < 62708b9452f8eb77513115b17c4f8d1a22ebf843
Linux · Linux
- affected 6.0
- unaffected < 6.0
- unaffected 6.1.149 – ≤ 6.1.*
- unaffected 6.6.103 – ≤ 6.6.*
- unaffected 6.12.44 – ≤ 6.12.*
- unaffected 6.16.4 – ≤ 6.16.*
- unaffected 6.17 – ≤ *

References (8)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

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Record last updated 7 Oct 2026, 17:56 UTC.