CVE-2026-56732 in Zammad
Summary
by MITRE • 09/25/2026
Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2, vulnerability in Zammad's HTML sanitization allows injection of specific HTML elements into ticket bodies. When another user views the crafted ticket, the injected element can trigger a logout request, terminating the viewer's session. This vulnerability is fixed in 7.0.2.
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Analysis
by VulDB Data Team • 09/25/2026
The vulnerability identified within Zammad versions prior to 7.0.2 represents a critical failure in input validation and output encoding mechanisms, specifically concerning HTML sanitization processes. As an open-source helpdesk and customer support system, Zammad relies heavily on the integrity of ticket bodies which are often composed by multiple users with varying levels of technical expertise. The core flaw lies in the application's inability to adequately filter or escape specific HTML elements when they are submitted as part of a ticket description or comment. This deficiency allows an attacker who has access to create or edit tickets to inject malicious markup that bypasses existing security controls, effectively turning standard text fields into vectors for cross-site scripting and session manipulation attacks.
From a technical perspective, the vulnerability stems from insufficient sanitization logic that fails to recognize or neutralize specific HTML tags capable of triggering side effects beyond simple visual rendering. While many systems focus on preventing script execution via JavaScript injection, this flaw highlights a broader oversight where structural elements are permitted if they do not immediately appear malicious but can be leveraged for state-changing actions. When another user views the crafted ticket within their browser session, the injected HTML element is rendered by the client-side environment. This rendering process triggers an unintended action, specifically a logout request that terminates the viewer's active authentication session. This mechanism exploits the trust relationship between the web application and the user agent, allowing unauthenticated or low-privilege actions to be performed on behalf of the victim without their explicit consent through standard UI interactions like clicking buttons.
The operational impact of this vulnerability is significant for organizations relying on Zammad for customer support operations. The primary consequence is a denial-of-service effect targeting individual users rather than the entire system infrastructure, as each affected user must re-authenticate to regain access. However, in high-volume environments where agents handle numerous tickets simultaneously, repeated exploitation can lead to substantial productivity losses and operational friction. Furthermore, this vulnerability undermines the principle of least privilege by allowing one user to disrupt another's workflow without requiring elevated permissions or complex exploit chains. It also poses a risk to session integrity, as forced logouts may interfere with audit trails or active support interactions that require continuous authentication states.
This issue aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting (XSS). More specifically, it relates to stored XSS variants where malicious content is saved on the server and executed when retrieved by other users. In terms of offensive security frameworks, this vulnerability maps to MITRE ATT&CK technique T1059 Command and Control via Application Layer Protocol or more accurately T1204 User Execution if considering the social engineering aspect required for victims to view the ticket. The forced logout mechanism also touches upon session management weaknesses often categorized under CWE-613, though the primary vector remains input validation failure.
To mitigate this vulnerability, organizations running Zammad versions prior to 7.0.2 must immediately upgrade to version 7.0.2 or later where the sanitization logic has been corrected to properly handle and escape these specific HTML elements. Until an upgrade is feasible, administrators should consider implementing web application firewall rules that detect and block requests containing suspicious HTML tags known to trigger session termination actions. Additionally, enforcing strict Content Security Policy headers can help mitigate the impact by restricting the sources from which scripts or certain element behaviors are allowed to execute. Regular security audits of custom integrations and plugins within Zammad are also recommended to ensure no similar sanitization gaps exist in extended functionality modules that interact with ticket bodies.