The vulnerability in RoundCube Webmail involves improper handling of SVG documents containing animate tags, which can be manipulated to perform cross-site scripting (XSS) attacks. SVG (Scalable Vector Graphics) files can embed animate tags that control animations within the graphic. The flaw allows attackers to inject malicious scripts via these animate tags, which are then executed in the context of the victim's browser when the SVG is rendered in the webmail interface. This can lead to session hijacking, credential theft, or unauthorized actions performed on behalf of the user. The vulnerability was patched in December 2025, indicating that the issue was identified and fixed before widespread exploitation. However, the lack of known exploits in the wild suggests that attackers may still be developing or testing attack vectors. The vulnerability does not require prior authentication, increasing the attack surface, but successful exploitation requires the victim to open or interact with a crafted SVG file or email containing such content. The medium severity rating reflects the moderate impact on confidentiality and integrity, with no direct impact on availability. The absence of a CVSS score necessitates a severity assessment based on the nature of the vulnerability and its exploitation potential.

If exploited, this vulnerability could allow attackers to execute arbitrary scripts within the context of a user's webmail session, potentially leading to theft of session cookies, credentials, or other sensitive information. It may also enable attackers to perform actions on behalf of the user, such as sending emails or modifying account settings, undermining user trust and organizational security. The impact is particularly significant for organizations relying on RoundCube Webmail for internal or external communications, as compromised accounts can facilitate further attacks, including phishing or lateral movement within networks. While the vulnerability does not directly affect system availability, the breach of confidentiality and integrity can have severe operational and reputational consequences. The medium severity reflects that exploitation requires user interaction and crafted content delivery but does not necessitate complex attack chains or elevated privileges.

Organizations should immediately verify that all RoundCube Webmail instances are updated to the latest patched version released in December 2025. Beyond patching, implement strict input validation and sanitization for all SVG and other image content uploaded or displayed within the webmail interface. Deploy Content Security Policy (CSP) headers to restrict script execution and reduce the risk of XSS attacks. Educate users to be cautious when opening emails with embedded SVG content or attachments from untrusted sources. Monitor webmail logs for unusual activities indicative of exploitation attempts. Consider disabling or restricting SVG rendering in the webmail client if feasible. Regularly audit and update webmail configurations to minimize attack surfaces and ensure security best practices are followed.