CVE-2025-4011 is a cross-site scripting (XSS) vulnerability identified in the Redmine project management software versions 6.0.0 through 6.0.3. The vulnerability resides in the Custom Query Handler component, specifically involving the manipulation of the 'Name' argument. An attacker can remotely exploit this flaw by injecting malicious scripts into the input fields that handle this argument. When a victim user views the affected page or query, the injected script executes in their browser context, potentially allowing the attacker to steal session cookies, perform actions on behalf of the user, or redirect the user to malicious sites. The vulnerability requires no authentication but does require user interaction, such as viewing a crafted query or page. The CVSS 4.0 base score is 5.1, indicating a medium severity level. The vulnerability does not affect confidentiality directly but impacts integrity and availability to a limited extent by enabling script execution in the victim’s browser. The issue is addressed by upgrading to Redmine version 6.0.4, which includes patches that sanitize or properly handle the 'Name' argument to prevent script injection. No known exploits are reported in the wild as of the publication date, but the vulnerability’s remote attack vector and low complexity make it a credible risk, especially in environments where Redmine is widely used for project tracking and collaboration.

For European organizations, the impact of this XSS vulnerability can be significant in environments where Redmine is used extensively for project management, issue tracking, and collaboration. Successful exploitation could lead to session hijacking, unauthorized actions performed under the victim’s credentials, and potential phishing attacks targeting internal users. This can result in data integrity issues, unauthorized disclosure of sensitive project information, and disruption of workflows. Since Redmine is often integrated with other tools and may contain links to internal resources, the vulnerability could be leveraged as a pivot point for broader attacks within an organization’s network. The medium severity rating suggests that while the vulnerability is not critical, it still poses a tangible risk to confidentiality and integrity, particularly in organizations with high-value projects or sensitive data. The requirement for user interaction means that social engineering or targeted phishing may be used to increase the likelihood of exploitation. European organizations with regulatory obligations around data protection (e.g., GDPR) must consider the reputational and compliance risks associated with such vulnerabilities.

1. Immediate upgrade of all Redmine instances to version 6.0.4 or later to apply the official patch addressing CVE-2025-4011. 2. Implement strict input validation and output encoding on all user-supplied data, especially in custom query parameters, to prevent injection of malicious scripts. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers accessing Redmine. 4. Conduct user awareness training to recognize suspicious links or queries that could trigger XSS attacks. 5. Regularly audit and monitor Redmine logs for unusual query parameters or access patterns that may indicate attempted exploitation. 6. If possible, restrict access to Redmine interfaces to trusted networks or via VPN to reduce exposure to remote attackers. 7. Integrate Redmine with Single Sign-On (SSO) and multi-factor authentication (MFA) to limit the impact of session hijacking. 8. Use web application firewalls (WAFs) with rules tuned to detect and block XSS payloads targeting Redmine endpoints. These measures, combined with patching, provide layered defense against exploitation.