# CVE-2026-52931: batman-adv: tp_meter: avoid use of uninit sender vars

> A malicious ACK packet can trigger undefined behavior in the Linux kernel's batman-adv module, potentially causing a crash or code execution.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 24 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-90561, BELL-CVE-2026-52931, DEBIAN-CVE-2026-52931, GHSA-xwx9-x5x2-3cmw, ROOT-OS-DEBIAN-11-CVE-2026-52931, ROOT-OS-DEBIAN-12-CVE-2026-52931, ROOT-OS-UBUNTU-2204-CVE-2026-52931, ROOT-OS-UBUNTU-2404-CVE-2026-52931, UBUNTU-CVE-2026-52931

## What is CVE-2026-52931?

CVE-2026-52931 is a critical use after free vulnerability in Linux kernel, published on 24 Jun 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:

batman-adv: tp_meter: avoid use of uninit sender vars

batadv_tp_recv_ack() and batadv_tp_stop() are only valid for tp_vars in the
BATADV_TP_SENDER role. When called with a BATADV_TP_RECEIVER role, it
proceeds to read sender-only members that were never initialized, leading
to undefined behavior.

This can be triggered when a node that is currently acting as a receiver in
an ongoing tp_meter session receives a malicious ACK packet.

Guard against this by checking tp_vars->role immediately after the
lookup and bailing out if it is not BATADV_TP_SENDER, before any of
those members are accessed.

Weakness: CWE-457 (Use of Uninitialized Variable)

## Which versions are affected by CVE-2026-52931?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52931?

Apply the vendor's patch.

## Is CVE-2026-52931 being exploited?

There is no known exploitation of CVE-2026-52931 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-2026-52931 and fix it if it is affected.

What it is: CVE-2026-52931 is a critical use after free vulnerability in Linux kernel, published on 24 Jun 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-2026-52931 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-2026-52931/ (Markdown: https://insights.sbomify.com/CVE-2026-52931/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52931
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52931
- OSV: https://osv.dev/vulnerability/CVE-2026-52931

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52931/
Summaries are generated and may contain mistakes; the official description above is the record.