CVE-2018-7302 in Tiki
Summary
by MITRE
Tiki 17.1 allows upload of a .PNG file that actually has SVG content, leading to XSS.
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Analysis
by VulDB Data Team • 01/07/2020
The vulnerability identified as CVE-2018-7302 affects Tiki 17.1 content management system and represents a critical security flaw in file upload validation mechanisms. This issue stems from inadequate content type verification during file processing, specifically targeting image file uploads that are expected to be in png format but can actually contain malicious svg content. The vulnerability resides in the application's file handling logic where it fails to properly validate the actual content of uploaded files against their declared file extensions, creating a pathway for attackers to bypass security controls through file format manipulation.
The technical implementation of this vulnerability exploits the inherent flexibility of web browsers in interpreting different file formats. When a user uploads a file with a .png extension but containing svg code, the system accepts it as a legitimate image file due to insufficient validation checks. The svg content can include embedded javascript code that executes when the file is rendered in a web browser, creating a cross-site scripting attack vector. This occurs because the application's security model assumes that file extensions accurately represent file content, failing to perform proper content analysis or magic number verification that would detect the actual file type regardless of its extension.
The operational impact of CVE-2018-7302 extends beyond simple data theft or service disruption, as it enables attackers to execute arbitrary javascript code within the context of authenticated user sessions. This vulnerability can be exploited to steal session cookies, perform unauthorized actions on behalf of users, redirect victims to malicious sites, or even escalate privileges within the application. The attack surface is particularly concerning because it can be leveraged by attackers to compromise user accounts and potentially gain access to sensitive data stored within the Tiki application. The vulnerability affects both regular users and administrators, making it a significant concern for organizations relying on Tiki for content management and collaboration.
Security mitigations for this vulnerability should focus on implementing robust file validation mechanisms that go beyond simple extension checks. Organizations should deploy content type verification using magic number detection, MIME type validation, and proper file format analysis to ensure that uploaded files match their claimed extensions. The implementation should include strict input sanitization, file content inspection, and proper error handling for malformed uploads. Additionally, implementing Content Security Policy headers and sandboxing mechanisms can provide additional defense-in-depth layers. This vulnerability aligns with CWE-434 which addresses insecure file upload handling, and maps to ATT&CK technique T1059.007 for scripting languages and T1566 for phishing with malicious attachments, emphasizing the need for comprehensive upload validation and user awareness training. Organizations should also consider implementing web application firewalls and regular security scanning to detect and prevent exploitation attempts.