# CVE-2026-109976: Clevis: clevis: integer underflow in pkcs#11 data socket handler crashes daemon on unbound client connection

> An integer underflow in Clevis PKCS#11 handler crashes the daemon on unbound connections, preventing LUKS decryption and causing denial of service.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/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:** 13 Oct 2026
- **Updated:** 14 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-109976, GHSA-vqch-3qxf-26cw, UBUNTU-CVE-2026-109976

## What is CVE-2026-109976?

CVE-2026-109976 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 13 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in the clevis PKCS#11 pin. The clevis-pkcs11-afunix-socket-unlock daemon crashes when an AF_UNIX client connects to the data socket without a bound address, due to an integer underflow in the getpeername result handling. This causes a denial of service, preventing LUKS disk decryption from completing during boot.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-109976?


## How do I fix CVE-2026-109976?

Apply the vendor's patch.

## Is CVE-2026-109976 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109976 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109976 and fix it if it is affected.

What it is: CVE-2026-109976 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 13 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109976 exists.

Affected product: Red Hat Enterprise Linux 10. 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-2026-109976/ (Markdown: https://insights.sbomify.com/CVE-2026-109976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109976
- OSV: https://osv.dev/vulnerability/CVE-2026-109976

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-109976/
Summaries are generated and may contain mistakes; the official description above is the record.