CVE-2017-7799 in Firefox
Summary
by MITRE
JavaScript in the "about:webrtc" page is not sanitized properly being assigned to "innerHTML". Data on this page is supplied by WebRTC usage and is not under third-party control, making this difficult to exploit, but the vulnerability could possibly be used for a cross-site scripting (XSS) attack. This vulnerability affects Firefox < 55.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability identified as CVE-2017-7799 represents a cross-site scripting flaw in Mozilla Firefox browsers prior to version 55. This issue resides within the browser's handling of JavaScript content within the "about:webrtc" page mechanism. The WebRTC implementation in Firefox provides diagnostic information about WebRTC functionality through this special about: page, which displays technical details about the browser's WebRTC capabilities and usage statistics. The vulnerability stems from improper sanitization of JavaScript code when this information is assigned to the innerHTML property of DOM elements, creating an avenue for malicious script execution.
The technical flaw manifests when WebRTC-related data is processed and displayed within the about:webrtc page context. While the data originates from the browser's own WebRTC implementation and not from external third-party sources, the lack of proper input sanitization creates a potential vector for XSS attacks. The innerHTML property assignment bypasses normal security mechanisms that would typically prevent script execution, allowing malicious JavaScript code embedded within the WebRTC data to be executed in the context of the about:webrtc page. This represents a classic DOM-based cross-site scripting vulnerability where the attack vector is the improper handling of trusted but unvalidated data within the browser's own interface components.
The operational impact of this vulnerability is significant despite its exploitation difficulty. While the attack requires specific conditions and cannot be easily triggered through normal user interaction, it demonstrates a critical flaw in Firefox's security architecture. The vulnerability affects all versions of Firefox prior to 55, representing a substantial user base that would be exposed to potential exploitation. Attackers could potentially leverage this vulnerability to execute arbitrary JavaScript code in the context of the about:webrtc page, potentially leading to session hijacking, data theft, or further exploitation of the browser's security model. The complexity of exploitation makes it less likely to be used in widespread attacks, but the potential for targeted attacks against specific user groups remains a concern.
This vulnerability maps to CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications. The issue also aligns with ATT&CK technique T1211 which covers exploitation of vulnerabilities for privilege escalation and code execution. The affected Firefox versions were particularly vulnerable because they lacked proper sanitization of data before innerHTML assignment, creating a direct pathway for malicious script injection. Security researchers noted that while the data source was not directly controllable by third parties, the browser's failure to sanitize the data properly created a security gap that could be exploited through sophisticated attack vectors. The vulnerability highlights the importance of input validation and output sanitization even within browser-internal components where data sources might appear trusted. Organizations should ensure immediate patching of affected Firefox versions and consider implementing additional security measures such as content security policies to mitigate potential exploitation risks. The fix implemented in Firefox 55 involved proper sanitization of WebRTC data before assignment to innerHTML properties, demonstrating the critical importance of secure coding practices in browser security implementations.