CVE-2026-73208

NameCVE-2026-73208
DescriptionAn attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs1146018

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
dovecot (PTS)bookworm, bookworm (security)1:2.3.19.1+dfsg1-2.1+deb12u6vulnerable
trixie (security), trixie1:2.4.1+dfsg1-6+deb13u6vulnerable
forky, sid1:2.4.5+dfsg1-2fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
dovecotsource(unstable)1:2.4.5+dfsg1-11146018

Notes

https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0003.html#cve-2026-73208-auth-db-oauth2-aud-claim-used-as-fallback-for-missing-scope-claim

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