# CVE-2026-72227: batman-adv: mcast: avoid OOB read of num_dests header

> An out-of-bounds read in the batman-adv multicast module allows attackers to read kernel memory or cause a denial of service.

- **Severity:** High 8.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72227, DEBIAN-CVE-2026-72227, GHSA-h862-94w3-mqrr, UBUNTU-CVE-2026-72227

## What is CVE-2026-72227?

CVE-2026-72227 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 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:

batman-adv: mcast: avoid OOB read of num_dests header

Before the access to struct batadv_tvlv_mcast_tracker's num_dests, it is
attempted to check whether enough space is actually in the network header.
But instead of using offsetofend() to check for the whole size (2) which
must be accessible, offsetof() of is called. The latter is always returning
0. The comparison with the network header length will always return that
enough data is available - even when only 1 or 0 bytes are accessible.

Instead of using offsetofend(), use the more common check for the whole
header.

## Which versions are affected by CVE-2026-72227?


## How do I fix CVE-2026-72227?

Apply the vendor's patch.

## Is CVE-2026-72227 being exploited?

There is no known exploitation of CVE-2026-72227 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72227 and fix it if it is affected.

What it is: CVE-2026-72227 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 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-2026-72227 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-2026-72227/ (Markdown: https://insights.sbomify.com/CVE-2026-72227/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72227
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72227
- OSV: https://osv.dev/vulnerability/CVE-2026-72227

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72227/
Summaries are generated and may contain mistakes; the official description above is the record.