CVE-2025-41055 is a stored Cross-Site Scripting (XSS) vulnerability identified in appRain CMF version 4.0.5. This vulnerability arises from improper neutralization of user input during web page generation, specifically within the 'data[Addon][layouts]' and 'data[Addon][layouts_except]' parameters in the /apprain/developer/addons/update/dialogs endpoint. The flaw allows an authenticated user with limited privileges to inject malicious scripts that are stored on the server and subsequently executed in the browsers of users who access the affected pages. The vulnerability is classified under CWE-79, indicating improper input validation leading to XSS. The CVSS 4.0 base score is 5.1 (medium severity), reflecting that the attack vector is network-based with low attack complexity, no privileges required beyond authentication, and requires user interaction (e.g., a victim visiting a maliciously crafted page). The vulnerability does not impact confidentiality, integrity, or availability directly but can be leveraged for session hijacking, credential theft, or other client-side attacks. No public exploits have been reported yet, and no patches are currently available, increasing the urgency for mitigation. The vulnerability affects a specific version (4.0.5) of appRain CMF, a content management framework used for building web applications, which may be deployed in various organizational contexts.

For European organizations using appRain CMF 4.0.5, this vulnerability poses a moderate risk primarily to web application security and user trust. Exploitation could lead to unauthorized script execution in users' browsers, enabling attackers to steal session cookies, perform actions on behalf of users, or redirect users to malicious sites. This can result in data leakage, reputational damage, and potential regulatory non-compliance under GDPR if personal data is compromised. Since the vulnerability requires authentication, internal users or attackers with compromised credentials could exploit it, increasing the risk of insider threats or lateral movement within networks. The lack of a patch means organizations must rely on other mitigations to reduce exposure. The impact is particularly significant for sectors with high web application usage such as finance, healthcare, and government services in Europe, where trust and data protection are critical. Additionally, the stored nature of the XSS means that the malicious payload persists, increasing the window of opportunity for exploitation.

1. Immediate mitigation should include restricting access to the affected endpoint (/apprain/developer/addons/update/dialogs) to only highly trusted administrators and monitoring for unusual activity. 2. Implement strict input validation and output encoding on the 'data[Addon][layouts]' and 'data[Addon][layouts_except]' parameters to neutralize potentially malicious scripts. 3. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers. 4. Conduct thorough code reviews and penetration testing focusing on input handling in the appRain CMF environment. 5. If possible, upgrade to a later, patched version of appRain CMF once available or apply vendor-provided patches promptly. 6. Educate authenticated users about phishing and social engineering risks that could facilitate exploitation. 7. Monitor web application logs for suspicious input patterns or error messages related to these parameters. 8. Use Web Application Firewalls (WAFs) with custom rules to detect and block XSS payloads targeting these parameters. 9. Isolate critical systems running appRain CMF to minimize lateral movement if exploitation occurs.