# CVE-2026-59845: Libssh: libssh: denial of service via unchecked proxycommand fork() failure

> An attacker can cause local denial of service in libssh by triggering a fork failure during ProxyCommand execution, leading to invalid process ID handling.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 21 Jul 2026
- **Updated:** 1 Sep 2026
- **Also known as:** AZL-93249, BELL-CVE-2026-59845, DEBIAN-CVE-2026-59845, ECHO-d722-762e-9126, GHSA-97fp-2vw9-q5jg, UBUNTU-CVE-2026-59845

## What is CVE-2026-59845?

CVE-2026-59845 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service.

Weakness: CWE-390 (Detection of Error Condition Without Action)

## Which versions are affected by CVE-2026-59845?

It affects 3 products.


Products: Libssh Libssh, Redhat Enterprise Linux, Redhat Hardened Images.

## How do I fix CVE-2026-59845?

Apply the vendor's patch.

## Is CVE-2026-59845 being exploited?

There is no known exploitation of CVE-2026-59845 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2026-59851](https://insights.sbomify.com/CVE-2026-59851/): Libssh: libssh: authentication bypass via missing gssapi principal check (high 8.8)
- [CVE-2025-5987](https://insights.sbomify.com/CVE-2025-5987/): Libssh: invalid return code for chacha20 poly1305 with openssl backend (high 8.1)
- [CVE-2025-14821](https://insights.sbomify.com/CVE-2025-14821/): Libssh: libssh: insecure default configuration leads to local man-in-the-middle attacks on windows (high 7.8)
- [CVE-2012-4560](https://insights.sbomify.com/CVE-2012-4560/): Memory corruption in n/a (high 7.5)
- [CVE-2012-4562](https://insights.sbomify.com/CVE-2012-4562/): Integer overflow in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59845 and fix it if it is affected.

What it is: CVE-2026-59845 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-59845 in the wild and no public exploit code.

Affected product: Redhat Enterprise 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-2026-59845/ (Markdown: https://insights.sbomify.com/CVE-2026-59845/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59845
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59845
- OSV: https://osv.dev/vulnerability/CVE-2026-59845

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59845/
Summaries are generated and may contain mistakes; the official description above is the record.