CVE-2020-36307 in Redmine
Summary
by MITRE • 04/06/2021
Redmine before 4.0.7 and 4.1.x before 4.1.1 has stored XSS via textile inline links.
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Analysis
by VulDB Data Team • 04/10/2021
The vulnerability identified as CVE-2020-36307 represents a stored cross-site scripting flaw affecting Redmine versions prior to 4.0.7 and 4.1.x versions before 4.1.1. This issue specifically manifests within the textile markup processing functionality, where inline links containing malicious script code can be persisted in the application's database and subsequently executed when other users view the affected content. The vulnerability stems from inadequate input sanitization and output encoding mechanisms within the textile parser implementation. Attackers can exploit this weakness by crafting malicious textile syntax that includes javascript payloads within link destinations or descriptions, which then get stored in the database and rendered to other users without proper sanitization. This stored nature of the vulnerability makes it particularly dangerous as the malicious code persists across multiple user sessions and can affect any user who accesses the compromised content.
The technical exploitation of this vulnerability involves understanding how textile markup language processes inline links and the specific parsing mechanisms that fail to properly escape or validate user-provided content. When users create textile links using the format [link text](url) or similar syntax, the application fails to adequately sanitize the URL portion of the link, allowing malicious payloads to be stored directly in the database. This flaw operates at the application layer and specifically affects the rendering pipeline where textile content gets converted to html for display. The vulnerability can be categorized under CWE-79 as Cross-Site Scripting, with elements of CWE-20 as Improper Input Validation. The attack surface is expanded when considering that Redmine is widely used for project management and issue tracking, making it a prime target for attackers seeking to compromise user sessions or exfiltrate sensitive information from organizational networks.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal cookies, redirect users to malicious sites, or even execute more sophisticated attacks such as credential harvesting. When combined with other vulnerabilities or attack vectors within the Redmine application, this stored XSS can serve as a foothold for more extensive compromise of the system. The vulnerability affects not just individual users but can potentially impact entire organizations that rely on Redmine for collaborative development and project management activities. Attackers can leverage this weakness to target administrators or users with elevated privileges, potentially leading to complete system compromise. The persistence of stored XSS makes it particularly challenging to detect and remediate, as malicious content remains embedded in the application's data stores until proper sanitization is implemented.
Organizations should prioritize immediate patching of affected Redmine installations to address this vulnerability, ensuring that all systems are updated to version 4.0.7 or 4.1.1 respectively. Additionally, implementing proper input validation and output encoding mechanisms within the textile processing pipeline can provide defense-in-depth measures. Security teams should conduct comprehensive audits of all textile content within the application to identify and remediate any existing malicious payloads. The implementation of Content Security Policy headers can provide an additional layer of protection against script execution, although this should not be relied upon as the sole mitigation. Regular security scanning and monitoring of user-generated content should be implemented to detect potential exploitation attempts. Organizations using custom textile extensions or plugins should verify that these components also properly sanitize user input to prevent similar vulnerabilities from being introduced through third-party integrations. The vulnerability highlights the importance of maintaining up-to-date software versions and implementing robust input validation practices across all user-facing application components.