# CVE-2026-80639: cxl/test: Fix __fortify_panic

> A false positive buffer overflow check in the CXL test module causes a kernel panic, leading to local denial of service.

- **Severity:** Not scored
- **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:** 28 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-80639, GHSA-gm6m-26p9-v4r9, UBUNTU-CVE-2026-80639

## What is CVE-2026-80639?

CVE-2026-80639 is a denial of service vulnerability in Linux, published on 28 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:

cxl/test: Fix __fortify_panic

Fix a runtime assertion in setup_xor_mapping(). Fortify complains that it
is potentially overflowing the xormaps array per __counted_by(nr_maps).
Quiet the false positive by initializing @nr_maps earlier.

 memcpy: detected buffer overflow: 32 byte write of buffer size 0
 WARNING: lib/string_helpers.c:1036 at __fortify_report+0x4d/0xa0, CPU#8: modprobe/2728
 Call Trace:
  __fortify_panic+0xd/0xf
  setup_xor_mapping+0x6c/0xa0 [cxl_translate]

[ dj: Fixed up @nr_entries to @nr_maps in commit log. ]

## Which versions are affected by CVE-2026-80639?


## How do I fix CVE-2026-80639?

Apply the vendor's patch.

## Is CVE-2026-80639 being exploited?

There is no known exploitation of CVE-2026-80639 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80639 and fix it if it is affected.

What it is: CVE-2026-80639 is a denial of service vulnerability in Linux, published on 28 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-2026-80639 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-2026-80639/ (Markdown: https://insights.sbomify.com/CVE-2026-80639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80639
- OSV: https://osv.dev/vulnerability/CVE-2026-80639

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80639/
Summaries are generated and may contain mistakes; the official description above is the record.