CVE-2025-46655 is a medium-severity vulnerability affecting CodiMD, an open-source collaborative markdown editor developed by HackMD. The vulnerability stems from improper protection of alternate paths (CWE-424) related to the handling of uploaded SVG documents containing JavaScript. CodiMD versions through 2.5.4 implement a Content Security Policy (CSP)-based mechanism designed to prevent cross-site scripting (XSS) attacks via SVG uploads. However, this protection can be bypassed in scenarios where the SVG files are stored on different origins, such as AWS S3 buckets, which do not enforce or insert CSP headers. This architectural choice can lead to a situation where malicious JavaScript embedded in SVG files executes in the context of the application, potentially allowing an attacker to perform limited XSS attacks. The vulnerability requires network access (AV:N), has a high attack complexity (AC:H), requires low privileges (PR:L), and does not require user interaction (UI:N). The scope is changed (S:C), indicating that the vulnerability affects components beyond the vulnerable component itself. The impact on confidentiality and integrity is low (C:L, I:L), with no impact on availability (A:N). No known exploits are currently reported in the wild, and no patches have been linked yet. The issue is partly due to user architectural decisions, specifically the use of AWS S3 without CSP header enforcement, which is considered a misconfiguration or user error rather than a direct software flaw. This vulnerability highlights the risks of relying solely on CSP for XSS protection when content is served from different origins without consistent security headers.

For European organizations using CodiMD, especially those leveraging AWS S3 or similar third-party storage services for hosting user-uploaded SVG content, this vulnerability could lead to limited XSS attacks. While the confidentiality and integrity impacts are rated low, successful exploitation could allow attackers to execute malicious scripts in the context of the application, potentially leading to session hijacking, data leakage of user-generated content, or manipulation of collaborative documents. Given the collaborative nature of CodiMD, such attacks could undermine trust in shared documents and disrupt workflows. The lack of availability impact reduces the risk of denial-of-service, but the integrity and confidentiality concerns remain relevant, particularly for organizations handling sensitive or regulated data. The medium CVSS score reflects the moderate risk, but the actual impact depends heavily on deployment architecture and the presence of mitigating controls. Organizations with strict data protection requirements under GDPR should be cautious, as even limited data exposure or manipulation could have compliance implications.

1. Enforce CSP headers consistently across all origins serving SVG content, including AWS S3 buckets or any other external storage. This can be achieved by configuring AWS CloudFront distributions or S3 bucket policies to inject appropriate CSP headers. 2. Avoid hosting untrusted JavaScript or SVG content on different origins without security controls. If external storage is necessary, implement strict content validation and sanitization before upload. 3. Upgrade to the latest version of CodiMD once patches addressing this vulnerability are released. 4. Implement additional server-side validation to detect and reject SVG files containing JavaScript or other executable content. 5. Monitor application logs and user activity for unusual behavior indicative of XSS exploitation attempts. 6. Educate developers and system architects on the risks of relying solely on CSP for XSS protection, especially in multi-origin architectures. 7. Consider deploying a Web Application Firewall (WAF) with rules to detect and block malicious SVG payloads. 8. Review and tighten AWS IAM policies and bucket permissions to minimize exposure of stored content.