CVE-2016-1967 in Firefox
Summary
by MITRE
Mozilla Firefox before 45.0 does not properly restrict the availability of IFRAME Resource Timing API times, which allows remote attackers to bypass the Same Origin Policy and obtain sensitive information via crafted JavaScript code that leverages history.back and performance.getEntries calls after restoring a browser session. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-7207.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1967 represents a significant security flaw in Mozilla Firefox versions prior to 45.0 that undermines the browser's fundamental security model. This issue specifically targets the Resource Timing API implementation within IFRAME elements, creating a mechanism that allows malicious actors to circumvent the Same Origin Policy that serves as a cornerstone of web security. The vulnerability stems from an incomplete remediation of a previously discovered flaw, CVE-2015-7207, demonstrating how security fixes can sometimes introduce new attack vectors when not thoroughly validated. The exploitation technique relies on sophisticated JavaScript manipulation that leverages browser session restoration capabilities combined with performance timing APIs.
The technical execution of this vulnerability involves crafting malicious JavaScript code that takes advantage of the browser's history management system and performance measurement functions. Attackers can utilize the history.back() method in conjunction with performance.getEntries() calls to gather timing information from different origins within the same browsing session. This creates a scenario where sensitive timing data that should be restricted to the same origin can be accessed across different domains, effectively bypassing the security boundaries that separate web resources. The flaw specifically affects how Firefox handles Resource Timing API data within IFRAME contexts, allowing cross-origin information leakage through timing-based side-channel attacks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a method to reconstruct user browsing patterns and potentially identify sensitive activities. When combined with other timing-based attacks, this vulnerability could enable adversaries to infer user behavior, track navigation patterns, and even identify specific web applications or services being accessed. The ability to bypass the Same Origin Policy through timing information leakage creates a persistent threat that can be exploited across multiple sessions and browsing contexts, making it particularly dangerous for users who maintain long-lived browser sessions. This vulnerability affects not just individual users but also organizations that rely on Firefox for secure browsing environments.
Mitigation strategies for CVE-2016-1967 require immediate browser version updates to Firefox 45.0 or later, where the vulnerability has been properly addressed through comprehensive fixes to the Resource Timing API implementation. Organizations should implement security monitoring to detect potential exploitation attempts and ensure all Firefox installations are updated with the latest security patches. The fix addresses the root cause by properly restricting access to timing information within IFRAME contexts and strengthening the enforcement of Same Origin Policy boundaries. Security teams should also consider implementing additional browser hardening measures and monitoring for suspicious JavaScript behavior that might indicate attempts to exploit similar timing-based vulnerabilities. This vulnerability aligns with CWE-200 (Information Exposure) and represents a variant of the broader class of timing-based side-channel attacks that have been documented in various security frameworks including ATT&CK's T1074.001 (Data Staged) and T1566.001 (Phishing).