# CVE-2026-59848: Libssh: libssh: denial of service via sftp responses with unknown request ids

> A malicious SFTP server can cause client-side denial of service in libssh by sending responses with unknown request IDs, leading to unbounded memory growth.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 21 Jul 2026
- **Updated:** 1 Sep 2026
- **Also known as:** AZL-93240, BELL-CVE-2026-59848, DEBIAN-CVE-2026-59848, ECHO-b7fc-a7ac-f445, GHSA-4h4r-q9xg-gfmm, UBUNTU-CVE-2026-59848

## What is CVE-2026-59848?

CVE-2026-59848 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in libssh. A malicious SFTP server can send responses for unknown request IDs that libssh clients keep queued indefinitely, causing unbounded memory growth and client-side denial of service.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-59848?

It affects 3 products.


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

## How do I fix CVE-2026-59848?

Apply the vendor's patch.

## Is CVE-2026-59848 being exploited?

There is no known exploitation of CVE-2026-59848 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-2026-59848 and fix it if it is affected.

What it is: CVE-2026-59848 is a medium-severity denial of service vulnerability in Redhat Enterprise Linux, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-59848 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-2026-59848/ (Markdown: https://insights.sbomify.com/CVE-2026-59848/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59848
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59848
- OSV: https://osv.dev/vulnerability/CVE-2026-59848

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59848/
Summaries are generated and may contain mistakes; the official description above is the record.