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


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** AZL-110963, BELL-CVE-2026-99071, DEBIAN-CVE-2026-99071, GHSA-66g6-r4v9-4xgm, UBUNTU-CVE-2026-99071

## What is CVE-2026-99071?

CVE-2026-99071 is a vulnerability in Linux, published on 23 Oct 2026. 

### Official 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.

## Which versions are affected by CVE-2026-99071?


## How do I fix CVE-2026-99071?

Upgrade to a fixed version.

## Is CVE-2026-99071 being exploited?

There is no known exploitation of CVE-2026-99071 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99071 and fix it if it is affected.

What it is: CVE-2026-99071 is a vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99071 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-99071/ (Markdown: https://insights.sbomify.com/CVE-2026-99071/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99071
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99071
- OSV: https://osv.dev/vulnerability/CVE-2026-99071

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99071/
Summaries are generated and may contain mistakes; the official description above is the record.