# CVE-2026-81666: Integer overflow in Red Hat Enterprise Linux 10

> An integer overflow in Corosync allows remote attackers to crash cluster nodes on 32-bit systems via crafted network packets, causing denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/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:** 4 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-81666, GHSA-8297-6g53-8gp5, UBUNTU-CVE-2026-81666

## What is CVE-2026-81666?

CVE-2026-81666 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an out-of-bounds memory access that crashes the Corosync daemon. This results in a denial of service for the affected cluster node. The overflow does not occur on 64-bit systems, where the length calculation is correctly performed in 64-bit arithmetic.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-81666?


## How do I fix CVE-2026-81666?

Apply the vendor's patch.

## Is CVE-2026-81666 being exploited?

There is no known exploitation of CVE-2026-81666 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81666 and fix it if it is affected.

What it is: CVE-2026-81666 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 4 Sep 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-2026-81666 in the wild and no public exploit code.

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-2026-81666/ (Markdown: https://insights.sbomify.com/CVE-2026-81666/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81666
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81666
- OSV: https://osv.dev/vulnerability/CVE-2026-81666

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81666/
Summaries are generated and may contain mistakes; the official description above is the record.