CVE-2026-40205

Name	CVE-2026-40205
Description	An attacker that holds an OAuth2 token granting only part of the required scopes can authenticate, because when more than one scope is required in the configuration, the remote token validation paths accept a token that carries only one of them, while the local token validation path correctly requires all of them. The configured authorization policy is not enforced, so a token that was granted only part of the required permissions is accepted where it should have been rejected. Use local token validation where tokens can be validated locally. 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-2026-40205-oauth2-passdb-scope-enforcement-bypass-via-or-semantics-in-remote-validation-path
Same fixes for CVE-2026-40205 and CVE-2026-73208
Fixed by: https://github.com/dovecot/core/commit/4aa93054b6c9e4d0503e1cb78be36b389d2af98c
Fixed by: https://github.com/dovecot/core/commit/8518e3f62183b462bef645977b48af32e6701f6f
Fixed by: https://github.com/dovecot/core/commit/91b7a86a20f805301e8ea15715b246040c4d8cd9