CVE-2026-73208: open-xchange gmbh ox dovecot ce Improper Authentication

Vulnerability summary

CVE-2026-73208 is a high (CVSS 7.4) Improper Authentication vulnerability in open-xchange gmbh ox dovecot ce. EPSS estimates a 0.31% chance of exploitation in the next 30 days, higher than 22.7% of scored vulnerabilities.

Timeline

1. 28-08-2026
   PublishedVulnerability first disclosed.
2. 28-08-2026
   Last modifiedVulnerability information updated.

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.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.