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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-58051?
It affects 1 product.
Linux distribution packages (3)
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 include Libssh2 Libssh2.
How do I fix CVE-2026-58051?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
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 libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
- CVE-2026-66032 libssh2 Double-Free Heap Corruption via sftp_open()
- CVE-2026-66033 libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation
- CVE-2026-58050 libssh2 - Integer Overflow in publickey Subsystem Attribute Allocation
- CVE-2025-15661 libssh2 - Heap Buffer Over-read via sftp_symlink() in sftp.c
Sources
Also known as ALPINE-CVE-2026-58051, AZL-91385, AZL-97395, AZL-97437, BELL-CVE-2026-58051, DEBIAN-CVE-2026-58051 and 5 more.