CVE-2018-16629 in Subrion CMS
Summary
by MITRE
panel/uploads/#elf_l1_XA in Subrion CMS v4.2.1 allows XSS via an SVG file with JavaScript in a SCRIPT element.
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Analysis
by VulDB Data Team • 06/30/2020
The vulnerability CVE-2018-16629 represents a cross-site scripting flaw within Subrion CMS version 4.2.1 that specifically affects the file upload functionality in the panel area. This issue manifests when users upload SVG files through the elf_l1_XA upload handler, which processes media uploads in the administrative interface. The vulnerability stems from insufficient input validation and sanitization of uploaded files, particularly those with the svg extension that may contain embedded javascript code within script elements. The affected component exists within the panel/uploads/#elf_l1_XA path, indicating this is part of the content management system's administrative upload functionality designed for handling various media file types including images and documents. This particular vulnerability allows attackers to inject malicious javascript code directly into SVG files that are then processed and stored by the CMS system.
The technical implementation of this vulnerability involves the improper handling of SVG file uploads where the system fails to properly sanitize or validate the contents of uploaded files before storing them in the system. When an SVG file containing a script element with javascript code is uploaded through the designated upload interface, the CMS does not adequately filter or escape the content, allowing the malicious script to persist within the system. This represents a classic case of insufficient input sanitization where the system trusts user-provided content without proper validation. The vulnerability is classified as a cross-site scripting attack because the malicious javascript code can be executed in the context of other users who view the uploaded SVG file, potentially leading to session hijacking, data theft, or further exploitation of the compromised system. This flaw directly relates to CWE-79 which defines improper neutralization of input during web page generation, specifically in the context of HTML and script content.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with a potential foothold for more sophisticated attacks within the CMS environment. An attacker who successfully exploits this vulnerability could gain unauthorized access to the administrative interface, modify content, steal user sessions, or even escalate privileges within the system. The persistence of the malicious script within uploaded files means that the attack vector remains active until the compromised file is removed or the vulnerability is patched. This vulnerability is particularly dangerous because SVG files are commonly used for images and are often trusted by web browsers, making the attack more likely to succeed without user suspicion. The attack surface is limited to the panel upload functionality but can have significant consequences for the overall security posture of the CMS installation.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization of all uploaded files, particularly those with potentially dangerous extensions like svg. Organizations should immediately apply the vendor-provided patch or upgrade to a patched version of Subrion CMS to resolve this issue. Additionally, implementing proper file type validation, content inspection, and sanitization of SVG files before storage can prevent similar issues from occurring. Security measures should include configuring the web application to reject or strip javascript content from SVG files, implementing proper content security policies, and regularly auditing uploaded files for malicious content. This vulnerability also highlights the importance of following secure coding practices as outlined in the OWASP Top Ten and MITRE ATT&CK framework, specifically addressing the prevention of XSS attacks through proper input validation and output encoding. Organizations should also implement network segmentation and monitoring to detect unauthorized file uploads and potential exploitation attempts. The recommended approach includes deploying web application firewalls, implementing proper access controls, and conducting regular security assessments to identify and remediate similar vulnerabilities across the entire application stack.