# CVE-2026-58051: libssh2 - Free of Uninitialized Pointer in publickey List Cleanup

> A malicious SSH server can trigger a use-after-free in libssh2 clients via malformed publickey responses, potentially leading to code execution or crashes.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** ALPINE-CVE-2026-58051, AZL-91385, AZL-97395, AZL-97437, BELL-CVE-2026-58051, DEBIAN-CVE-2026-58051, ECHO-b4f1-7845-4dda, GHSA-c5f3-hwj2-xp5p, JLSEC-2026-663, RHSA-2026:46535, UBUNTU-CVE-2026-58051

## What is CVE-2026-58051?

CVE-2026-58051 is a high-severity use after free vulnerability in libssh2, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libssh2 through 1.11.1 grows its publickey list with SSH2_REALLOC but does not zero-initialize new entries before parsing populates them, so a parse failure reaching the cleanup path leaves libssh2_publickey_list_free operating on an uninitialized entry. A malicious SSH server offering the publickey subsystem can use a malformed response to make cleanup free an uninitialized, attacker-influenceable attrs pointer in a connecting libssh2 client.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2026-58051?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libssh2` | Red Hat:hummingbird:1 | All versions | 0:1.11.1-10.1.hum1 |
| `libssh2-devel` | Red Hat:hummingbird:1 | All versions | 0:1.11.1-10.1.hum1 |
| `libssh2-docs` | Red Hat:hummingbird:1 | All versions | 0:1.11.1-10.1.hum1 |

Products: Libssh2 Libssh2.

## How do I fix CVE-2026-58051?

Apply the vendor's patch.

## Is CVE-2026-58051 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58051 exists.

## Other vulnerabilities in libssh2

- [CVE-2026-55200](https://insights.sbomify.com/CVE-2026-55200/): libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c (critical 9.2)
- [CVE-2026-66032](https://insights.sbomify.com/CVE-2026-66032/): libssh2 Double-Free Heap Corruption via sftp_open() (high 8.7)
- [CVE-2026-66033](https://insights.sbomify.com/CVE-2026-66033/): libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation (high 8.7)
- [CVE-2026-58050](https://insights.sbomify.com/CVE-2026-58050/): libssh2 - Integer Overflow in publickey Subsystem Attribute Allocation (high 8.3)
- [CVE-2025-15661](https://insights.sbomify.com/CVE-2025-15661/): libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c (high 8.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58051 and fix it if it is affected.

What it is: CVE-2026-58051 is a high-severity use after free vulnerability in libssh2, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58051 exists.

Affected product: libssh2. 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-2026-58051/ (Markdown: https://insights.sbomify.com/CVE-2026-58051/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58051
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58051
- OSV: https://osv.dev/vulnerability/CVE-2026-58051

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58051/
Summaries are generated and may contain mistakes; the official description above is the record.