CVE-2020-26030: Zammad

Critical severity, CVSS 9.8. EPSS: 1.4% chance of exploitation in the next 30 days.

An issue was discovered in Zammad before 3.4.1. There is an authentication bypass in the SSO endpoint via a crafted header, when SSO is not configured. An attacker can create a valid and authenticated session that can be used to perform any actions in the name of other users.

Affected products

• Zammad Zammad: from 1.0.0, before 3.4.1 (fixed in 3.4.1)

Published 2020-12-28. Last modified 2026-06-17.