Live › vulnerability › CVE-2025-39682
Go to dashboardLinux kernel kTLS (net/tls/tls_sw.c) bug: when a zero-length TLS 1.3 record is the first record taken from rx_list, recvmsg() mishandles record-type changes and the zero-copy path, so a later record is queued or processed wrongly. NVD rates it local, low-privilege, with high confidentiality and availability impact (memory disclosure or DoS). It is in CISA KEV (added 2026-09-18). Affected: kernels 6.0 up to the fixed stable releases. Only systems that use kernel TLS receive (the tls module with sockets set to the tls ULP) are reachable.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 19:11 UTC, 5h before NVD. All times on this page are UTC.
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.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| Linux Kernel | vendor | >= 6.0, < 6.1.149; >= 6.2, < 6.6.103; >= 6.7, < 6.12.44; >= 6.13, < 6.16.4; 6.17-rc1, 6.17-rc2 | 6.1.149, 6.6.103, 6.12.44, 6.16.4, 6.17-rc3 |
| linux kernel | vendor | >= 6.0, < 6.1.149 | 6.1.149 |
| linux kernel | vendor | >= 6.2, < 6.6.103 | 6.6.103 |
| linux kernel | vendor |
| >= 6.7, < 6.12.44 |
| 6.12.44 |
| linux kernel | vendor | >= 6.13, < 6.16.4 | 6.16.4 |
| linux kernel | vendor | = 6.17 | – |
| debian linux | vendor | = 11.0 | – |
| siemens simatic cn 4100 firmware | vendor | < 5.0 | 5.0 |
| Linux Kernel | vendor | – | – |
uname -r and compare with the fixed versionslsmod | grep tls, and cat /proc/net/tls_stat (non-zero TlsRxSw/TlsRxDevice counters mean kTLS receive is active)6.1.149, 6.6.103, 6.12.44, 6.16.4 or 6.17 and later (fix in 6.17-rc3)Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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
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.
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