# CVE-2026-43042: mpls: add seqcount to protect the platform_label{,s} pair

> A race condition in the Linux kernel MPLS subsystem allows out-of-bounds memory access, potentially leading to code execution or denial of service.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-85377, BELL-CVE-2026-43042, DEBIAN-CVE-2026-43042, GHSA-j45g-66j9-q94m, ROOT-OS-DEBIAN-11-CVE-2026-43042, ROOT-OS-DEBIAN-12-CVE-2026-43042, ROOT-OS-DEBIAN-13-CVE-2026-43042, ROOT-OS-UBUNTU-2204-CVE-2026-43042, ROOT-OS-UBUNTU-2404-CVE-2026-43042, UBUNTU-CVE-2026-43042

## What is CVE-2026-43042?

CVE-2026-43042 is a high-severity vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

mpls: add seqcount to protect the platform_label{,s} pair

The RCU-protected codepaths (mpls_forward, mpls_dump_routes) can have
an inconsistent view of platform_labels vs platform_label in case of a
concurrent resize (resize_platform_label_table, under
platform_mutex). This can lead to OOB accesses.

This patch adds a seqcount, so that we get a consistent snapshot.

Note that mpls_label_ok is also susceptible to this, so the check
against RTA_DST in rtm_to_route_config, done outside platform_mutex,
is not sufficient. This value gets passed to mpls_label_ok once more
in both mpls_route_add and mpls_route_del, so there is no issue, but
that additional check must not be removed.

Weakness: CWE-125 (Out-of-bounds Read), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-43042?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43042?

Apply the vendor's patch.

## Is CVE-2026-43042 being exploited?

There is no known exploitation of CVE-2026-43042 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-2026-43042 and fix it if it is affected.

What it is: CVE-2026-43042 is a high-severity vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43042 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-2026-43042/ (Markdown: https://insights.sbomify.com/CVE-2026-43042/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43042
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43042
- OSV: https://osv.dev/vulnerability/CVE-2026-43042

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43042/
Summaries are generated and may contain mistakes; the official description above is the record.