CVE-2025-39682
tls: fix handling of zero-length records on the rx_list
Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
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.
CISA notes
This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f; https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677; https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9; https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e; https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2025-39682
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.
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation Context
as of October 15, 2026- CISA added CVE-2025-39682 to the KEV catalog 378 days after its CVE record was published. The median for entries added in 2026 so far is 14 days.
- It is one of 31 Linux Kernel entries in the CISA KEV catalog, and one of 8 added in 2026.
- Its current EPSS score (2.9%) is higher than that of 12% of CISA KEV entries.
Affected Products
| Vendor | Product | Affected versions |
|---|---|---|
| Linux | Linux Linux | 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to <2902c3ebcca52ca845c03182000e8d71d3a5196f 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to <c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to <3439c15ae91a517cf3c650ea15a8987699416ad9 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to <29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to <62708b9452f8eb77513115b17c4f8d1a22ebf843 |
| Linux | Linux Linux | 6.0 0 to <6.0 (unaffected) 6.1.149 to 6.1.* (unaffected) 6.6.103 to 6.6.* (unaffected) 6.12.44 to 6.12.* (unaffected) 6.16.4 to 6.16.* (unaffected) 6.17 to * (unaffected) |
References
6 Links- https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
- https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
- https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
- https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
- https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
Record Details
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