Bug 2496768 (CVE-2026-12064)

Summary:	CVE-2026-12064 curl: curl: SSH host verification bypass when using schemeless URLs with SFTP/SCP
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:	akhatavk, aos-team-art-private, asdas, dbosanac, dpaolell, jdelft, jreimann, jupierce, lgarciaa, mbiarnes, mdessi, mrizzi, pcattana, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sdawley, sghai, sidsharm, suppawar, vlaad, 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 user invokes curl with a schemeless URL and specifies SFTP (SSH File Transfer Protocol) or SCP (Secure Copy Protocol) as the default protocol, the tool layer fails to initialize critical SSH security options. This bypasses host verification, allowing curl to connect to an unverified SSH remote host without alerting the user. This could enable an attacker to intercept or manipulate data through 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:	2497523, 2497524, 2497526
Bug Blocks:

Description OSIDB Bzimport 2026-07-03 07:02:04 UTC

When a user invokes curl using a schemeless URL combined with
`--proto-default` sftp (or scp), a disconnect occurs between the tool layer
and libcurl. The tool layer incorrectly infers the URL scheme, which
erroneously bypasses the initialization of critical SSH security options like
CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 and CURLOPT_SSH_KNOWNHOSTS. Conversely, the
libcurl runtime successfully honors CURLOPT_DEFAULT_PROTOCOL and establishes
the connection via SFTP/SCP as specified. Because the tool layer skipped the
security configuration, these SSH host verification options are silently
omitted, causing curl to connect to an unverified SSH remote host without
throwing an error.

Comment 2 errata-xmlrpc 2026-08-17 04:40:24 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:55450 https://access.redhat.com/errata/RHSA-2026:55450