# CVE-2025-39839: batman-adv: fix OOB read/write in network-coding decode

> An out-of-bounds read and write in the batman-adv network-coding decode function allows attackers to potentially execute code or cause a denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Sep 2025
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-67514, AZL-74826, BELL-CVE-2025-39839, DEBIAN-CVE-2025-39839, GHSA-2j47-jhvw-fgmm, ROOT-OS-DEBIAN-11-CVE-2025-39839, ROOT-OS-DEBIAN-12-CVE-2025-39839, ROOT-OS-DEBIAN-13-CVE-2025-39839, ROOT-OS-UBUNTU-2204-CVE-2025-39839, ROOT-OS-UBUNTU-2404-CVE-2025-39839, UBUNTU-CVE-2025-39839

## What is CVE-2025-39839?

CVE-2025-39839 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 19 Sep 2025. 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: fix OOB read/write in network-coding decode

batadv_nc_skb_decode_packet() trusts coded_len and checks only against
skb->len. XOR starts at sizeof(struct batadv_unicast_packet), reducing
payload headroom, and the source skb length is not verified, allowing an
out-of-bounds read and a small out-of-bounds write.

Validate that coded_len fits within the payload area of both destination
and source sk_buffs before XORing.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-39839?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-39839?

Apply the vendor's patch.

## Is CVE-2025-39839 being exploited?

There is no known exploitation of CVE-2025-39839 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39839 and fix it if it is affected.

What it is: CVE-2025-39839 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 19 Sep 2025. 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-2025-39839 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-39839/ (Markdown: https://insights.sbomify.com/CVE-2025-39839/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39839
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39839
- OSV: https://osv.dev/vulnerability/CVE-2025-39839

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39839/
Summaries are generated and may contain mistakes; the official description above is the record.