Security Advisory


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

Security Advisory Details

  • ID: ZAA-2023-06
  • Date: 2023-12-06
  • Title: Denial of Service
  • Severity: low
  • Product: Zammad 6.1.x
  • Fixed in: Zammad 6.2.0
  • References:
    --> CVE-2023-50455

Vulnerability Descriptions

Denial of Service

Due to a missing rate limiting in the 'email address verification' feature of Zammad, an attacker could send many requests for a known address to cause Denial Of Service by many generated emails which would also spam the victim.

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:

Or just update your Zammad if installed via OS package manager.

Additional information

Online version of this advisory:

Please send remarks on security issues exclusively to

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