Bug 2496758 (CVE-2026-9547)

Summary:	CVE-2026-9547 curl: curl: Man-in-the-middle attack via SSH host key bypass
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	dbosanac, jreimann, mdessi, mrizzi, pcattana, rhel-process-autobot, sdawley, 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 curl. When a libcurl-based application uses SCP:// or SFTP:// for transfers and employs the CURLOPT_SSH_KEYFUNCTION callback, it may silently accept an untrusted server. This occurs if the server's host key type differs from the one stored in the known_hosts file. The callback mechanism fails to enforce the host key restriction, enabling a connection to an untrusted server and risking a man-in-the-middle attack.	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:	2497409, 2497410, 2497411
Bug Blocks:

Description OSIDB Bzimport 2026-07-03 07:01:34 UTC

When a libcurl-based application performs transfers via `SCP://` or `SFTP://`
and utilizes the `CURLOPT_SSH_KEYFUNCTION` callback, it may silently accept an
untrusted server. This vulnerability occurs when a server presents a host key
type that does not match the specific key type already recorded for that host
in the `known_hosts` file. Instead of rejecting the mismatch, the callback
mechanism fails to properly enforce the restriction, allowing the connection
to succeed without warning and risking a potential man-in-the-middle attack.