CVE-2025-46654 is a medium-severity vulnerability affecting HackMD's CodiMD product up to version 2.2.0. The vulnerability stems from improper protection of alternate paths (CWE-424) in the application's handling of uploaded content. Specifically, CodiMD employs a Content Security Policy (CSP) mechanism designed to prevent cross-site scripting (XSS) attacks by restricting the execution of uploaded JavaScript files. However, this protection can be bypassed by uploading an HTML file that references an uploaded JavaScript (.js) file. This indirect referencing allows an attacker to execute malicious scripts despite the CSP restrictions, potentially leading to limited confidentiality and integrity impacts. The vulnerability does not require user interaction but does require low-level privileges to upload files, and it can be exploited remotely over the network. The CVSS 3.1 base score is 4.9, reflecting a medium severity with a vector indicating network attack vector, high attack complexity, low privileges required, no user interaction, and a scope change. The impact primarily affects confidentiality and integrity, with no direct impact on availability. No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability was publicly disclosed on April 26, 2025.

For European organizations using CodiMD, particularly those leveraging it for collaborative documentation and note-taking, this vulnerability could allow attackers to execute unauthorized scripts within the context of the application. This could lead to unauthorized access to sensitive information, data manipulation, or session hijacking, compromising confidentiality and integrity. Although the attack complexity is high and requires some privileges, the network attack vector and lack of required user interaction increase the risk in environments where multiple users have upload permissions. Organizations in sectors such as education, research, and enterprises relying on CodiMD for internal collaboration may face risks of data leakage or tampering. Given the scope change indicated by the CVSS vector, exploitation could affect resources beyond the initially vulnerable component, potentially impacting interconnected systems or services. However, the absence of availability impact and the medium severity score suggest that while the threat is significant, it is not critical. The lack of known exploits in the wild provides a window for mitigation before active exploitation occurs.

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Restrict file upload permissions strictly to trusted users and roles, minimizing the number of accounts that can upload files. 2) Implement server-side validation to block or sanitize HTML files that reference external JavaScript files, preventing the bypass of CSP protections. 3) Enhance CSP policies to include stricter directives such as disallowing inline scripts and restricting script sources to trusted domains only. 4) Monitor and audit uploaded content regularly for suspicious files or patterns indicative of exploitation attempts. 5) Isolate the CodiMD application environment using containerization or sandboxing to limit the impact of any successful exploit. 6) Stay updated with vendor advisories and apply patches promptly once available. 7) Employ Web Application Firewalls (WAFs) with custom rules to detect and block attempts to upload or serve malicious HTML/JS content. 8) Educate users about the risks of uploading untrusted files and enforce organizational policies accordingly. These targeted actions go beyond generic advice by focusing on the specific bypass vector and operational context of CodiMD deployments.