Bug 2498182 (CVE-2026-59849)

Summary:	CVE-2026-59849 libssh: libssh: denial of service via automatic certificate authentication loop
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	rhel-process-autobot, security-response-team, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	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.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2503674
Bug Blocks:

Description OSIDB Bzimport 2026-07-08 18:22:49 UTC

A flaw was found in libssh automatic certificate-based public key authentication. In ssh_userauth_publickey_auto() in src/auth.c, the iterator over certificate candidates was not advanced correctly when configured certificates were missing or repeatedly rejected by the server. Under specific non-default certificate configurations, this could cause the client to restart the same authentication attempts indefinitely, leading to denial of service.

Comment 2 errata-xmlrpc 2026-08-17 20:53:22 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:55855 https://access.redhat.com/errata/RHSA-2026:55855