CVE-2026-63006 in Zammad
Summary
by MITRE • 09/25/2026
Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, attacker-controlled HTML in inbound emails or tickets could bypass the image URL sanitizer using path traversal sequences. When an authenticated agent views the content, the browser resolves the URL to a protected API endpoint and sends the request with the agent's session cookie, enabling side effects such as forced logout without any user interaction. This issue is fixed in version 7.1.2.
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Analysis
by VulDB Data Team • 09/25/2026
Zammad serves as a prominent open-source helpdesk and customer support platform designed to manage communication channels including email, chat, phone, and social media. The software relies heavily on web technologies to render ticket content for agents and administrators. A critical security flaw was identified in versions prior to 7.1.2 concerning the sanitization of HTML content within inbound emails and tickets. This vulnerability stems from an insufficient validation mechanism when processing image URLs embedded in rich text fields, allowing attackers to inject malicious payloads that bypass existing security filters through path traversal techniques.
The technical core of this vulnerability lies in the failure of the application's input sanitizer to properly normalize or reject URL paths containing directory traversal sequences such as dot-dot-slash characters. When an attacker crafts a ticket or email with an image tag utilizing these malformed URLs, the backend system fails to strip or escape the malicious path components before storing or rendering them. Consequently, when this content is processed for display, the browser interprets the raw URL structure rather than sanitizing it into a safe format. This lack of strict output encoding and input validation creates a pathway for Cross-Site Scripting (XSS) variants that specifically target session management mechanisms via image loading requests.
The operational impact of this vulnerability is significant due to its potential for causing denial-of-service conditions through forced authentication state changes. When an authenticated agent views the compromised ticket content, their browser automatically attempts to load the maliciously crafted image source. Because the URL points to a protected API endpoint within the Zammad application itself, the browser attaches the agent's active session cookies and other authentication credentials to this request as part of standard HTTP behavior for same-origin requests. This results in unintended side effects where the server processes actions intended only for authenticated users but triggered by an attacker-controlled payload without any direct user interaction beyond viewing the ticket.
A primary consequence demonstrated in security assessments is the ability to force a logout or trigger other state-changing API endpoints on behalf of the victim agent. By manipulating the request context, an attacker can effectively hijack the session's intended action vector. This not only disrupts the workflow of support staff but also undermines the integrity of the system by allowing untrusted input to execute privileged operations. The vulnerability essentially transforms a passive viewing action into an active exploitation event where the victim's browser becomes an unwitting proxy for malicious requests against their own authenticated account.
This flaw aligns with Common Weakness Enumeration (CWE) categories such as CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting, and specifically relates to improper sanitization of URL schemes or paths that leads to unintended execution context changes. In the context of the MITRE ATT&CK framework, this behavior maps to techniques involving client-side code injection and potentially session hijacking through automated browser requests. The attack vector is classified as remote with low complexity because it requires only an authenticated user to view a specific piece of content, making social engineering or prior access necessary but not requiring complex exploitation steps once the malicious ticket is created.
Mitigation for this vulnerability involves upgrading the Zammad installation to version 7.1.2 or later, where the developers have implemented stricter validation rules for image URLs and improved sanitization logic to prevent path traversal sequences from being processed as valid resource locators. Organizations running older versions should prioritize immediate patching to restore secure operation. Additionally, implementing a Content Security Policy (CSP) with strict directives regarding script sources and object loading can provide an additional layer of defense by restricting the browser's ability to execute or load resources from untrusted origins even if sanitization fails. Regular security audits focusing on input validation for rich text editors are also recommended to prevent similar issues in other modules of the application.