CVE-2016-6850 in OX AppSuite
Summary
by MITRE
An issue was discovered in Open-Xchange OX App Suite before 7.8.2-rev8. SVG files can be used as profile pictures. In case their XML structure contains iframes and script code, that code may get executed when calling the related picture URL or viewing the related person's image within a browser. Malicious script code can be executed within a user's context. This can lead to session hijacking or triggering unwanted actions via the web interface (sending mail, deleting data etc.).
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Analysis
by VulDB Data Team • 07/08/2019
The vulnerability CVE-2016-6850 represents a critical cross-site scripting flaw in Open-Xchange OX App Suite versions prior to 7.8.2-rev8, classified under CWE-79 Improper Neutralization of Input During Web Page Generation. This vulnerability arises from insufficient input validation and sanitization of SVG image files that users can upload as profile pictures. The flaw specifically manifests when SVG files contain embedded iframes and script elements within their XML structure, creating a vector for malicious code execution. The vulnerability is particularly dangerous because it leverages the inherent capabilities of SVG files to contain executable code, making it a sophisticated attack vector that bypasses traditional security measures.
The technical exploitation of this vulnerability occurs when a malicious user uploads an SVG profile picture containing embedded script tags or iframe elements that reference external malicious content. When other users view the profile picture or interact with the related person's image within a browser, the embedded code executes within the context of the victim's session. This execution context provides attackers with the ability to perform actions as if they were the legitimate user, potentially leading to session hijacking, unauthorized data access, or the triggering of unwanted actions through the web interface. The vulnerability operates at the intersection of web application security and SVG processing, making it particularly challenging to detect and prevent.
The operational impact of CVE-2016-6850 extends beyond simple data theft or corruption, as it enables attackers to manipulate user sessions and potentially gain unauthorized access to sensitive information. The vulnerability can be exploited through social engineering tactics where malicious users upload crafted SVG files to profile pictures, or through more sophisticated attacks that leverage the browser's handling of SVG content. This type of vulnerability aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: JavaScript, as it involves the execution of JavaScript code within a user's browser context. The attack chain typically involves initial access through profile picture upload, followed by code execution within the victim's session, potentially leading to privilege escalation or data exfiltration.
Mitigation strategies for CVE-2016-6850 require a multi-layered approach focusing on input validation, content sanitization, and proper file handling. Organizations should implement strict SVG validation that removes or neutralizes embedded script elements and iframes from uploaded files before processing. This approach aligns with security best practices outlined in the OWASP Top Ten and follows the principle of least privilege by ensuring that uploaded content cannot execute malicious code. The most effective solution involves updating to Open-Xchange OX App Suite version 7.8.2-rev8 or later, which includes proper input sanitization and validation mechanisms. Additionally, implementing Content Security Policy headers and using secure file upload validation libraries can provide additional protection against similar vulnerabilities in other applications.