Linux · Kernel
CVE-2025-39682
tls: fix handling of zero-length records on the rx_list
Qué es
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.
CISA: Linux Kernel contains an improper check for unusual or exceptional conditions vulnerability in the TLS receive path which allows a zero-length record retrieved from the rx_list to bypass the intended recvmsg() record-type handling, potentially causing subsequent TLS records to be processed using incorrect zero-copy and queuing assumptions. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.
Qué hacer
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.
Plazo para las agencias federales de EE. UU.: 21 de septiembre de 2026
- Añadida a la lista de CISA
- 18 de septiembre de 2026
- Publicada
- 5 de septiembre de 2025
- Gravedad
- Crítica 9,8 CVSS 3.1
- Probabilidad de ataques en los próximos 30 días (EPSS)
- 3,3% entre el 11,7% superior de todas las vulnerabilidades conocidas
- Debilidad
- CWE-754
- Más detalles
- NVD · CVE.org · CISA
Todas las referencias (5)
- 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
Más fallos explotados de Linux
| Añadido | Vulnerabilidad | Producto | Gravedad | Prob. de ataque |
|---|---|---|---|---|
| 18 sept 2026 | Race Condition | Kernel | Alto 7,8 | 1,6% |
| 18 sept 2026 | Out-of-Bounds Write | Kernel | Alto 8,8 | 0,9% |
| 27 ago 2026 | Unspecified | Kernel | Alto 7,8 | 0,7% |
| 26 ago 2026 | Out-of-Bounds Write | Kernel | Alto 7,8 | 8,9% |
| 2 jun 2026 | Improper Authentication | Kernel | Alto 7,8 | 5,5% |
| 1 may 2026 | Incorrect Resource Transfer Between Spheres | Kernel | Alto 7,8 | 98% |
| 26 ene 2026 | Integer Overflow | Kernel | Alto 7,8 | 15% |
| 6 oct 2025 | Heap Out-of-Bounds Write | Kernel | Alto 8,3 | 79% |
Fuentes: Known Exploited Vulnerabilities (CISA, dominio público), CVE records (cve.org) y EPSS (FIRST). La probabilidad de ataque es la estimación EPSS de que alguien intente explotar el fallo en los próximos 30 días.