CVE-2018-16630 in Kirby
Summary
by MITRE
Kirby v2.5.12 allows XSS by using the "site files" Add option to upload an SVG file.
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Analysis
by VulDB Data Team • 04/24/2020
The vulnerability CVE-2018-16630 represents a cross-site scripting vulnerability within Kirby CMS version 2.5.12 that arises from insecure handling of SVG file uploads through the "site files" add functionality. This flaw enables malicious actors to execute arbitrary JavaScript code within the context of a victim's browser session by uploading specially crafted SVG files that contain malicious script payloads. The vulnerability stems from insufficient input validation and sanitization of file uploads, particularly affecting the content management system's file handling mechanisms.
The technical implementation of this vulnerability occurs when the CMS processes SVG files without proper sanitization of embedded script elements or event handlers. SVG files inherently support scripting through javascript: protocols and embedded script tags that can be executed when the file is rendered in a web browser. The vulnerability specifically manifests in the "site files" section where administrators or users with appropriate privileges can upload files, but the system fails to strip or neutralize potentially malicious content within SVG metadata or embedded code sections. This allows attackers to craft SVG files containing malicious javascript that executes when the file is viewed or processed by the CMS.
The operational impact of this vulnerability extends beyond simple XSS attacks as it can enable attackers to perform session hijacking, steal sensitive information, redirect users to malicious sites, or even escalate privileges within the CMS environment. The vulnerability affects the entire user base of Kirby 2.5.12 installations, particularly administrators who have access to file upload functionality, making it a critical security concern for organizations relying on this content management system. The attack vector is relatively straightforward requiring only the ability to upload files to the CMS, which may be accessible to authenticated users or even unauthenticated users depending on the specific configuration.
Security mitigations for this vulnerability involve immediate patching to the affected Kirby CMS version, implementing comprehensive file validation and sanitization for all uploaded content, particularly SVG files. Organizations should deploy Content Security Policy headers to prevent execution of inline scripts and ensure proper file type restrictions are enforced. The vulnerability aligns with CWE-79 (Cross-site Scripting) and CWE-20 (Improper Input Validation) categories, representing a classic insecure file upload vulnerability that can be addressed through proper input validation and output encoding. Additionally, implementing the principle of least privilege and restricting file upload capabilities to only necessary administrative users can significantly reduce the attack surface. Organizations should also consider implementing web application firewalls to detect and block malicious file upload attempts, and regularly audit file upload functionality to ensure proper sanitization of all media content. The ATT&CK framework categorizes this vulnerability under T1059.007 (Scripting) and T1566.001 (Phishing via Social Engineering) as it enables attackers to execute malicious scripts and potentially deliver phishing payloads through compromised CMS instances.