# CVE-2026-55653: Memory corruption in Red Hat Enterprise Linux 10

> A malicious SSH server can cause a client-side denial of service via a double free in OpenSSH during FIPS mode DH-GEX validation.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 23 Jun 2026
- **Updated:** 29 Oct 2026
- **Also known as:** AZL-91200, CLSA-2026-1783694178, CLSA-2026-1783706054, ECHO-bc9c-5617-0a3c, GHSA-28f3-55mq-pp68, UBUNTU-CVE-2026-55653

## What is CVE-2026-55653?

CVE-2026-55653 is a medium-severity memory corruption vulnerability in OpenSSH, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-55653?

It affects 4 products.


Products: OpenSSH, Redhat Enterprise Linux, Redhat Hardened Images, Redhat Openshift Container Platform.

## How do I fix CVE-2026-55653?

Apply the vendor's patch.

## Is CVE-2026-55653 being exploited?

There is no known exploitation of CVE-2026-55653 in the wild and no public exploit code.

## Other vulnerabilities in OpenSSH

- [CVE-2003-0786](https://insights.sbomify.com/CVE-2003-0786/): Auth bypass in n/a (critical 10.0)
- [CVE-2003-0693](https://insights.sbomify.com/CVE-2003-0693/): Memory corruption in n/a (critical 10.0)
- [CVE-2002-0640](https://insights.sbomify.com/CVE-2002-0640/): Memory corruption in n/a (critical 10.0)
- [CVE-2001-0144](https://insights.sbomify.com/CVE-2001-0144/): Integer overflow in n/a (critical 10.0)
- [CVE-2000-0999](https://insights.sbomify.com/CVE-2000-0999/): Memory corruption in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55653 and fix it if it is affected.

What it is: CVE-2026-55653 is a medium-severity memory corruption vulnerability in OpenSSH, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-55653 in the wild and no public exploit code.

Affected product: OpenSSH. 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-2026-55653/ (Markdown: https://insights.sbomify.com/CVE-2026-55653/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55653
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55653
- OSV: https://osv.dev/vulnerability/CVE-2026-55653

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55653/
Summaries are generated and may contain mistakes; the official description above is the record.