CVE-2026-73208 Auth bypass in OX Dovecot CE
Attackers can authenticate using tokens with mismatched audience claims if scope claims are missing, bypassing authorization checks in Dovecot.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73208?
CVE-2026-73208 is a high-severity authentication bypass vulnerability in Open-Xchange GmbH OX Dovecot CE, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An 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.
Weakness: CWE-287
Which versions are affected by CVE-2026-73208?
How do I fix CVE-2026-73208?
Upgrade to a fixed version.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-73208 being exploited?
There is no known exploitation of CVE-2026-73208 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-73208, AZL-98295, DEBIAN-CVE-2026-73208, GHSA-856w-5q8f-fq73, UBUNTU-CVE-2026-73208.