# CVE-2025-71080: ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT

> A race condition in the Linux kernel IPv6 routing code under PREEMPT_RT can trigger a kernel BUG, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Jan 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-71080, DEBIAN-CVE-2025-71080, GHSA-gmq5-qgc7-64gv, ROOT-OS-DEBIAN-13-CVE-2025-71080, UBUNTU-CVE-2025-71080

## What is CVE-2025-71080?

CVE-2025-71080 is a high-severity vulnerability in Linux kernel, published on 13 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT

On PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the
current task can be preempted. Another task running on the same CPU
may then execute rt6_make_pcpu_route() and successfully install a
pcpu_rt entry. When the first task resumes execution, its cmpxchg()
in rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer
NULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding
mdelay() after rt6_get_pcpu_route().

Using preempt_disable/enable is not appropriate here because
ip6_rt_pcpu_alloc() may sleep.

Fix this by handling the cmpxchg() failure gracefully on PREEMPT_RT:
free our allocation and return the existing pcpu_rt installed by
another task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT
kernels where such races should not occur.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2025-71080?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-71080?

Apply the vendor's patch.

## Is CVE-2025-71080 being exploited?

There is no known exploitation of CVE-2025-71080 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71080 and fix it if it is affected.

What it is: CVE-2025-71080 is a high-severity vulnerability in Linux kernel, published on 13 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-71080 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-71080/ (Markdown: https://insights.sbomify.com/CVE-2025-71080/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71080
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71080
- OSV: https://osv.dev/vulnerability/CVE-2025-71080

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71080/
Summaries are generated and may contain mistakes; the official description above is the record.