CVE-2026-59851

Publication date 21 July 2026

Last updated 25 August 2026

Ubuntu priority

Cvss 3 Severity Score

Description

A flaw was found in libssh. On servers with GSSAPIKeyExchange enabled, the gssapi-keyex path does not verify whether the authenticated Kerberos principal is authorized for the requested local user, allowing authenticated clients to log in as arbitrary users.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libssh	26.04 LTS resolute	Not affected
	24.04 LTS noble	Not affected
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected

Notes

mdeslaur

Introduced in 0.12.0 with: https://git.libssh.org/projects/libssh.git/commit/?id=9044fcdb52c870f0036319945ac860054384b2c1

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
libssh	Upstream: ?id=732 Upstream: ?id=05d Upstream: ?id=f2f

Severity score breakdown

CVSS version: CVSS v3.0

Base score 8.8 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality impact	High
Integrity impact	High
Availability impact	High

Scores

Parameter	Value
Base score	8.8 · High
Exploitability score	-
Impact score	-

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H