Description


Uncontrolled eviction in the pending sign-in tables of the REST API in Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to make other users' OpenID Connect, SAML and passkey sign-ins fail. The routes that start a single sign-on and hand out a passkey sign-in challenge are reached without authentication and stored pending state in bounded tables that dropped their oldest entry when full, whoever had started it. An attacker who starts sign-ins a few times a second (about a hundred a second for passkeys) pushes every other user's pending sign-in out of the table before that user's browser returns, denying single sign-on and passkey sign-in for as long as the requests continue.

Related CPE's


Could not find any relations

Weaknesses



CWE-770

CVSS impact metrics


CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

5.3 · Medium

Information


Source identifier

[email protected]

Vulnerability status

Deferred

Published

2026-10-08T15:17:44.763Z

17 hours ago

Last modified

2026-10-08T21:02:43.860Z

12 hours ago