CVE-2026-12064

Name	CVE-2026-12064
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
curl (PTS)	bullseye	7.74.0-1.3+deb11u13	fixed
	bullseye (security)	7.74.0-1.3+deb11u16	fixed
	bookworm	7.88.1-10+deb12u15	vulnerable
	bookworm (security)	7.88.1-10+deb12u5	vulnerable
	trixie	8.14.1-2+deb13u4	vulnerable
	forky	8.20.0-5	vulnerable
	sid	8.21.0-2	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
curl	source	bullseye	(not affected)
curl	source	(unstable)	8.21.0~rc3-1

Notes

[trixie] - curl <no-dsa> (Minor issue)
[bookworm] - curl <postponed> (Minor issue; needs schemeless URL with --proto-default sftp/scp)
[bullseye] - curl <not-affected> (Vulnerable code introduced in 7.81.0; bullseye ships 7.74.0)
https://curl.se/docs/CVE-2026-12064.html
Introduced with: https://github.com/curl/curl/commit/18270893abdb19f0ca170c118f8a2847dbd304be (curl-7_81_0)
Fixed by: https://github.com/curl/curl/commit/ab3bb8cd8be8f9d4acb97da0418abc279182041e (rc-8_21_0-3, curl-8_21_0)