CVE-2026-56735

Description

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.

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Produits concernés

• zammad

Scores CVSS

Faiblesses (CWE)

• CWE-82

Références

• 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

Ailleurs

• NVD
• CVE.org
• CIRCL Vulnerability-Lookup
• CERT-FR
• GitHub Advisories