CVE-2026-59849

Publication date 21 July 2026

Last updated 25 August 2026

Ubuntu priority

Cvss 3 Severity Score

Description

A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libssh	26.04 LTS resolute	Vulnerable
	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 0.11.0 by: https://github.com/libssh/libssh-mirror/commit/aae1bc10588787e1fe15c84b9f8f76176ac8e603

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=d9f Upstream: ?id=2a4 Upstream: ?id=a54

Severity score breakdown

CVSS version: CVSS v3.0

Base score 3.1 · Low

Base metrics

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

Scores

Parameter	Value
Base score	3.1 · Low
Exploitability score	-
Impact score	-

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