CVE-2026-42395

Name	CVE-2026-42395
Description	A host listed as a trusted proxy can send forwarding information containing a NUL byte, which crashes the login process on the following login attempt. The login process is terminated, which can cause degradation or denial of service for logins. Deployments that do not configure trusted proxies are not affected. Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version. No publicly available exploits are known.
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)
References	DSA-6526-1
Debian Bugs	1146018

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
dovecot (PTS)	bookworm, bookworm (security)	1:2.3.19.1+dfsg1-2.1+deb12u6	vulnerable
	trixie	1:2.4.1+dfsg1-6+deb13u6	vulnerable
	trixie (security)	1:2.4.1+dfsg1-6+deb13u7	fixed
	forky	1:2.4.5+dfsg1-2	fixed
	sid	1:2.4.5+dfsg1-3	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
dovecot	source	trixie	1:2.4.1+dfsg1-6+deb13u7		DSA-6526-1
dovecot	source	(unstable)	1:2.4.5+dfsg1-1			1146018

Notes

https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0003.html#cve-2026-42395-single-nul-byte-xclient-forward-payload-crashes
Fixed by: https://github.com/dovecot/core/commit/0a1adbe37e03e859681bab6186494600b1c708ac
Fixed by: https://github.com/dovecot/core/commit/991780f2a9d567f9c2f4b136d96b0b35e1d8e9e1