CVE-2025-41056 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 related to the 'data[Addon][layouts]' and 'data[Addon][layouts_except]' parameters in the endpoint /apprain/developer/addons/update/hysontable. Because these parameters are not properly validated or sanitized, an authenticated attacker can 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, which pertains to improper input validation leading to XSS attacks. The CVSS v4.0 base score is 5.1, indicating a medium severity level. The vector details reveal that the attack can be performed remotely (AV:N) with low attack complexity (AC:L), requires low privileges (PR:L), and some user interaction (UI:P). The vulnerability does not affect confidentiality, integrity, or availability directly but can be leveraged to execute arbitrary scripts in the context of the victim's browser, potentially leading to session hijacking, credential theft, or unauthorized actions on behalf of the user. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in April 2025 and published in September 2025 by INCIBE, a recognized cybersecurity entity. Given the nature of stored XSS, the impact can be significant if exploited in environments with sensitive user data or administrative interfaces.

For European organizations using appRain CMF 4.0.5, this vulnerability poses a tangible risk, especially for those with web applications accessible to multiple authenticated users or administrators. Exploitation could allow attackers to execute malicious scripts in the browsers of legitimate users, potentially leading to session hijacking, unauthorized actions, or data theft. This is particularly critical for organizations handling sensitive personal data under GDPR, as exploitation could result in data breaches and regulatory penalties. Additionally, the presence of stored XSS in administrative or developer endpoints could enable attackers to escalate privileges or pivot within the network. The medium CVSS score reflects that while the vulnerability requires some user interaction and low privileges, the potential for abuse in multi-user environments is notable. European sectors such as finance, healthcare, and government, which often deploy content management frameworks like appRain CMF, could face reputational damage and operational disruption if targeted. Furthermore, the lack of a patch increases the window of exposure, necessitating immediate mitigation efforts.

1. Immediate mitigation should involve implementing strict input validation and output encoding on the affected parameters ('data[Addon][layouts]' and 'data[Addon][layouts_except]') to neutralize any malicious scripts. 2. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 3. Restrict access to the /apprain/developer/addons/update/hysontable endpoint to trusted administrators only, using network segmentation or IP whitelisting. 4. Monitor web application logs for unusual input patterns or repeated attempts to inject scripts. 5. Educate users and administrators about the risks of XSS and the importance of cautious interaction with web interfaces. 6. Engage with the vendor or community to obtain or develop patches or updates addressing this vulnerability. 7. Consider deploying Web Application Firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting these parameters. 8. Conduct regular security assessments and penetration tests focusing on input validation weaknesses in appRain CMF deployments.