CVE-2026-56735

Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2 and 7.1.0, zammad's HTML sanitizer (HtmlSanitizer::Strict) blocks external URLs in to prevent remote content loading, but the srcset attribute, also allowlisted for , is not subject to the same check. This oversight allows an attacker to embed arbitrary external URLs in the srcset attribute just by sending an e-mail, effectively bypassing the external content protection. When an agent views the ticket containing the malicious srcset, the browser will silently load the attacker-controlled URL, resulting in the leakage of the agent's IP address, User-Agent, Referer, and the exact time the ticket was viewed. HtmlSanitizer::Strict got extended to block external URLs in the srcset attribute of tags. This was done to prevent tracking pixels and external content loading, which could compromise user privacy. This issue is fixed in versions 7.0.2 and 7.1.0.

CVSS

No CVSS.

References

Link	Resource
https://github.com/zammad/zammad/commit/02c1ff8dc65961352dc047013bece9dff1f2ffb7
https://github.com/zammad/zammad/releases/tag/7.0.2
https://github.com/zammad/zammad/releases/tag/7.1.0
https://github.com/zammad/zammad/security/advisories/GHSA-7fwx-3xr4-qm6w

Configurations

No configuration.

History

25 Sep 2026, 18:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-25 18:17

Updated : 2026-09-28 14:45

NVD link : CVE-2026-56735

Mitre link : CVE-2026-56735

CVE.ORG link : CVE-2026-56735

JSON object : View

Products Affected

No product.

CWE

CWE-82

Improper Neutralization of Script in Attributes of IMG Tags in a Web Page

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