Zammad up to 7.1.1 HTML Sanitizer input validation

Summaryinfo

A vulnerability described as problematic has been identified in Zammad up to 7.1.1. This impacts an unknown function of the component HTML Sanitizer. Such manipulation leads to input validation. This vulnerability is listed as CVE-2026-63206. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Zammad up to 7.1.1. It has been rated as problematic. Affected by this issue is an unknown code block of the component HTML Sanitizer. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality. CVE summarizes:

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, zammad's HTML sanitizer, which blocks remote images in ticket articles and email views, can be bypassed using a shortened URL format that omits the double slash after the scheme (for example a shortened HTTP URL instead of a shortened HTTP URL). Modern browsers treat both forms as equivalent remote URLs. As a result, an attacker who sends a crafted email or ticket can cause the recipient's browser to silently load an image from an external server, revealing when and by whom the ticket was opened. Zammad's "remote content blocked" warning is not shown because the sanitizer does not recognize the shortened form as remote. This issue is fixed in version 7.1.2.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-63206 since 07/16/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available.

Upgrading to version 7.1.2 eliminates this vulnerability.

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Productinfo

Name

• Zammad

Version

• 7.1.0
• 7.1.1

License

• open-source

Website

• Product: https://github.com/zammad/zammad/

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