CVE-2026-75000 in Roundcube
Summary
by MITRE • 08/17/2026
In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, improper HTML/CSS sanitization of the SVG animate "by" attribute may lead to remote image blocking bypass, which in turn may lead to information disclosure or privilege escalation.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified in Roundcube Webmail versions prior to 1.6.18 and version 1.7.x prior to 1.7.3 stems from an insufficient sanitization of HTML content specifically targeting the SVG animate by attribute. This flaw allows attackers to inject maliciously crafted Scalable Vector Graphics (SVG) elements that contain animated properties capable of manipulating how external resources are loaded or rendered within the webmail interface. The core technical issue lies in the application's failure to strictly validate and sanitize dynamic attributes associated with SVG animation tags, which permits the execution of unintended side effects when these graphics are processed by the client-side browser engine rather than being stripped out as potentially dangerous content.
This improper sanitization directly facilitates a remote image blocking bypass mechanism. In typical webmail environments, security policies often restrict or block external images to prevent tracking pixels and other forms of passive information gathering. However, by exploiting the SVG animate by attribute, an attacker can construct payloads that trick the browser into loading external resources in ways that circumvent these built-in privacy protections. The animation attributes allow for complex rendering behaviors that may not be caught by standard static sanitization filters, effectively creating a loophole through which blocked content types are successfully retrieved and displayed to the end user.
The operational impact of this vulnerability is significant as it transitions from a mere display anomaly to a vector for serious security breaches such as information disclosure or privilege escalation. Once an attacker can bypass image blocking restrictions, they can deploy tracking pixels that report back sensitive metadata including the recipient's IP address, email client version, operating system details, and precise location data based on geolocation services accessed via the loaded resources. Furthermore, if this capability is combined with other vulnerabilities in the Roundcube application layer or exploited within a context where user actions lead to administrative functions, it could potentially aid in privilege escalation attacks by facilitating targeted phishing campaigns that appear legitimate due to the successful rendering of embedded malicious content.
From an industry standard perspective, this vulnerability aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting (XSS). Although the primary vector here is not direct script execution but rather resource manipulation via SVG attributes, the root cause remains the failure to properly sanitize user-supplied input before it is rendered in a web context. Additionally, this behavior maps to MITRE ATT&CK technique T1059.007, which involves JavaScript-based command and control or data exfiltration through browser-side scripting mechanisms that leverage legitimate application features for malicious purposes. The exploitation of SVG elements falls under the broader category of client-side code injection where visual rendering engines are abused to execute unintended logic.
To mitigate this risk, organizations running Roundcube Webmail must immediately upgrade to version 1.6.18 or later if using the stable branch, or version 1.7.3 and above for the development branch. These releases contain patches that enforce stricter validation rules on SVG attributes, ensuring that dynamic animation properties are either stripped entirely or strictly validated against a whitelist of safe values. Administrators should also consider implementing Content Security Policy headers to further restrict the sources from which external resources can be loaded within their webmail environment. Regular security audits and penetration testing focused on input sanitization logic in rich text editors and email rendering engines are recommended to identify similar weaknesses before they can be exploited by adversaries seeking to compromise user privacy or escalate privileges within the application ecosystem.