Bug 2498179 (CVE-2026-59846)

Summary:	CVE-2026-59846 libssh: libssh: information disclosure via ProxyCommand %r username expansion
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. A malicious username expanded through %r in ProxyCommand handling can inject shell metacharacters, exposing environment variables and causing unintended shell behavior.	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:	2503669
Bug Blocks:

Description OSIDB Bzimport 2026-07-08 18:22:44 UTC

A flaw was found in libssh username handling for ProxyCommand expansion. The ssh_check_username_syntax() validation path in src/misc.c used an incomplete dangerous-character filter for usernames expanded through %r. As a result, specially crafted usernames containing shell-significant characters could reach shell-evaluated ProxyCommand handling and influence shell expansion, exposing environment variables and causing unintended shell behavior. This issue affects clients that combine untrusted username input with ProxyCommand-style shell execution.

Comment 2 errata-xmlrpc 2026-08-17 20:53:26 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

Comment 3 errata-xmlrpc 2026-09-01 17:53:28 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:62217 https://access.redhat.com/errata/RHSA-2026:62217

Comment 4 errata-xmlrpc 2026-09-01 18:33:13 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:62218 https://access.redhat.com/errata/RHSA-2026:62218