tls: fix handling of zero-length records on the rx_list
Affects the Linux kernel TLS receive code from 6.0 onward, in the 6.0 to 6.16 series. Fixed in stable releases 6.1.149, 6.6.103, 6.12.44 and 6.16.4. No vendor severity rating is given; the CVSS score is 9.8 (critical).
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Fix
- Fixed in 6.1.149, 6.6.103, 6.12.44, 6.16.4, :2026-03-05
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: active
- Automatable: yes
- Technical impact: total
Summary
The Linux kernel's TLS receive path (kernel TLS, used for TLS offload to the kernel's recvmsg() handling) is affected. A zero-length TLS record taken from the receive queue can be mishandled, which may cause incorrect record-type processing during reads and lead to a kernel-level problem such as a crash or corrupted data delivery.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original 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.
Timeline
- CVE published
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CISA SSVC assessment
Exploitation: active · Automatable: yes · Technical impact: total
- CISA remediation deadline
Due date for US federal agencies to patch
- Record last updated
Affected versions
- Linux Linux
From 84c61fe1a75b4255df1e1e7c054c9e6d048da417 · fixed in 2902c3ebcca52ca845c03182000e8d71d3a5196f; From 84c61fe1a75b4255df1e1e7c054c9e6d048da417 · fixed in c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677; From 84c61fe1a75b4255df1e1e7c054c9e6d048da417 · fixed in 3439c15ae91a517cf3c650ea15a8987699416ad9; From 84c61fe1a75b4255df1e1e7c054c9e6d048da417 · fixed in 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e; From 84c61fe1a75b4255df1e1e7c054c9e6d048da417 · fixed in 62708b9452f8eb77513115b17c4f8d1a22ebf843
- Linux Linux
6.0
- KernelLinux
From 6.0.0 · fixed in 6.1.149; From 6.2.0 · fixed in 6.6.103; From 6.7.0 · fixed in 6.12.44; From 6.13.0 · fixed in 6.16.4
- :linux_kernel:Android
From :0 · fixed in :2026-03-05
References 5
Questions about CVE-2025-39682
What does this mean?
The kernel's TLS code mishandles a zero-length record when the first record of a read comes from the rx_list queue. The original fix missed this corner case.Source: git.kernel.org
Am I affected, and how do I check?
Linux kernel versions from 6.0 up to the fixed releases listed for each branch are in scope: 6.1.149, 6.6.103, 6.12.44 and 6.16.4. To check a system, run uname -r and compare the version against those branch fixes. The change was introduced in commit 84c61fe1a75b4255df1e1e7c054c9e6d048da417.Source: git.kernel.org
What should I do about it?
Move to a kernel release that includes the fix: 6.1.149, 6.6.103, 6.12.44, or 6.16.4 on the matching branch, or any later stable release. Use the stable kernel update from your distribution or kernel source.Source: git.kernel.org
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-09-18, which means it has evidence of attacks. No public exploit code is tracked.Source: cisa.gov, cve.now feed data