CVE-2023-42458 in Zope
Summary
by MITRE • 09/21/2023
Zope is an open-source web application server. Prior to versions 4.8.10 and 5.8.5, there is a stored cross site scripting vulnerability for SVG images. Note that an image tag with an SVG image as source is never vulnerable, even when the SVG image contains malicious code. To exploit the vulnerability, an attacker would first need to upload an image, and then trick a user into following a specially crafted link. Patches are available in Zope 4.8.10 and 5.8.5. As a workaround, make sure the "Add Documents, Images, and Files" permission is only assigned to trusted roles. By default, only the Manager has this permission.
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Analysis
by VulDB Data Team • 03/05/2026
The vulnerability identified as CVE-2023-42458 affects the Zope web application server, a widely used open-source platform for building dynamic web applications. This security flaw represents a stored cross-site scripting vulnerability specifically targeting SVG image handling within the Zope framework. The vulnerability exists in versions prior to 4.8.10 and 5.8.5, making installations of these older versions susceptible to malicious exploitation. The flaw is particularly concerning because SVG files, while typically safe for image display, can contain executable JavaScript code when improperly handled by web servers. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a critical security weakness in web applications. The ATT&CK framework categorizes this as a technique involving code injection through web application vulnerabilities, specifically targeting user sessions and potentially leading to complete system compromise.
The technical mechanism of exploitation involves a multi-step process where an attacker must first gain the ability to upload malicious content to the server, typically requiring the "Add Documents, Images, and Files" permission. Once uploaded, the attacker crafts a specially crafted link that, when followed by an unsuspecting user, triggers the execution of malicious JavaScript code embedded within the SVG file. This occurs because the Zope server fails to properly sanitize SVG content during processing, allowing potentially harmful code to persist and execute when the image is rendered in a user's browser. The vulnerability is distinct from typical XSS scenarios because it requires both upload capability and user interaction through a crafted link, making it a stored XSS rather than a reflected one. The attack vector demonstrates the importance of proper input validation and content sanitization in web applications, particularly for file upload handlers that process rich media formats.
The operational impact of this vulnerability extends beyond simple session hijacking to potentially enable complete system compromise. When exploited successfully, attackers can execute arbitrary JavaScript code in the context of a victim's browser session, potentially leading to data theft, privilege escalation, or further exploitation of the web application. The vulnerability is particularly dangerous because SVG files are commonly used in web applications for icons, logos, and complex graphics, making them frequent targets for malicious content. Organizations running vulnerable Zope installations face significant risk of unauthorized access and data breaches, especially if user roles have overly permissive file upload permissions. The default security configuration of Zope, which restricts the "Add Documents, Images, and Files" permission to Managers only, provides a baseline defense, but this protection is only effective if administrators properly configure role-based access controls.
Mitigation strategies for CVE-2023-42458 focus on both immediate remediation and long-term security hardening. The primary solution involves upgrading to Zope versions 4.8.10 or 5.8.5, which contain the necessary patches to address the SVG sanitization vulnerability. Organizations should prioritize this upgrade as a critical security measure, particularly for production environments handling sensitive data. As a temporary workaround, administrators should ensure that the "Add Documents, Images, and Files" permission is restricted to trusted roles only, preventing unauthorized users from uploading potentially malicious content. Additional defensive measures include implementing content security policies, conducting regular security audits of file upload handlers, and monitoring for unauthorized file uploads. The vulnerability highlights the importance of comprehensive security testing for web applications, particularly in areas involving user-generated content and rich media processing. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for exploitation attempts targeting similar vulnerabilities in their web infrastructure.