CVE-2026-55653

Name	CVE-2026-55653
Description	A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).
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
openssh (PTS)	bullseye	1:8.4p1-5+deb11u3	fixed
	bullseye (security)	1:8.4p1-5+deb11u7	fixed
	bookworm	1:9.2p1-2+deb12u10	fixed
	bookworm (security)	1:9.2p1-2+deb12u9	fixed
	trixie	1:10.0p1-7+deb13u4	fixed
	trixie (security)	1:10.0p1-7+deb13u2	fixed
	forky	1:10.3p1-5	fixed
	sid	1:10.4p1-1	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
openssh	source	(unstable)	(not affected)

- openssh <not-affected> (Only an issue with FIPS patch which is not in Debian/upstream)
https://bugzilla.redhat.com/show_bug.cgi?id=2462351