Security Advisory


· Please read carefully and check if the version of your Zammad system is affected by this vulnerability. Please send information regarding vulnerabilities in Zammad to: security at

Security Advisory Details

  • ID: ZAA-2020-20
  • Date: 09/22/2020
  • Title: Wrong authorization checks for impersonation requests via X-On-Behalf-Of
  • Severity: medium
  • Product: Zammad 1.0.x up to 3.4.0
  • Fixed in: Zammad 3.4.1, 3.5.0
  • References:
    --> CVE: 2020-26029

Vulnerability Descriptions

Wrong authorisation checks for impersonation requests via X-On-Behalf-Of

Zammad allows impersonation requests via the X-On-Behalf-Of header. This allows authorised users to perform actions in the name of other users. However, the authorisation checks for those requests are performed for the actual user and not the one given in the X-On-Behalf-Of header. This allows an attacker to gain access to information without proper authentication checks.

This vulnerability is fixed in the latest versions of Zammad and it is recommended to upgrade to one of these.

Fixed releases can be found at:

Additional information

Online version of this advisory:

Send all remarks to security issues to

Freuen Ihre Kunden sich schon auf die Service-Hotline?
Kostenlos testen!
Alle Neuigkeiten direkt in Ihrer Inbox!
Zum Newsletter anmelden