CVE-2025-39682

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

Critical 9.8
Exploited: added to CISA KEV 18 Sep 2026

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.

Key facts

Published: 5 Sep 2025
Last changed: 7 Oct 2026
Assigned by: Linux
KEV added: 18 Sep 2026
KEV fix due: 21 Sep 2026
EPSS: 3.312% likely to be exploited in the next 30 days, higher than 88.763% of CVEs (scores for 15 Nov 2026)
SSVC (CISA): Exploitation: active; Automatable: yes; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

9.8CVSS 3.1, Criticalfrom the CNA (Linux)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What to do

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 KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
Linux	Linux	Default status: unaffected 84c61fe1a75b4255df1e1e7c054c9e6d048da417 up to but excluding 2902c3ebcca52ca845c03182000e8d71d3a5196f (affected) 84c61fe1a75b4255df1e1e7c054c9e6d048da417 up to but excluding c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677 (affected) 84c61fe1a75b4255df1e1e7c054c9e6d048da417 up to but excluding 3439c15ae91a517cf3c650ea15a8987699416ad9 (affected) 84c61fe1a75b4255df1e1e7c054c9e6d048da417 up to but excluding 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e (affected) 84c61fe1a75b4255df1e1e7c054c9e6d048da417 up to but excluding 62708b9452f8eb77513115b17c4f8d1a22ebf843 (affected)
Linux	Linux	Default status: affected 6.0 (affected) 0 up to but excluding 6.0 (unaffected) 6.1.149 up to and including 6.1.* (unaffected) 6.6.103 up to and including 6.6.* (unaffected) 6.12.44 up to and including 6.12.* (unaffected) 6.16.4 up to and including 6.16.* (unaffected) 6.17 up to and including * (unaffected)