CVE-2016-5250 in Firefox
Summary
by MITRE
Mozilla Firefox before 48.0 allows remote attackers to obtain sensitive information about the previously retrieved page via Resource Timing API calls.
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Analysis
by VulDB Data Team • 03/16/2019
The vulnerability identified as CVE-2016-5250 affects Mozilla Firefox versions prior to 48.0 and represents a significant information disclosure flaw within the browser's Resource Timing API implementation. This vulnerability enables remote attackers to extract sensitive information about previously accessed web pages through carefully crafted API calls that should not have been accessible to malicious actors. The Resource Timing API is designed to provide performance metrics for web page resources, but in this case it was improperly exposing confidential data about the browser's navigation history and resource loading patterns.
The technical flaw stems from inadequate access controls within Firefox's implementation of the Resource Timing API specification. When a web page makes Resource Timing API calls, the browser should only expose timing information for resources that the page itself has access to or has loaded. However, the vulnerability allowed attackers to query timing data for resources from previous pages that were not directly accessible to the current browsing context, effectively creating a cross-site information leakage channel. This flaw particularly impacts the navigation timing data and resource timing information that should remain isolated to prevent unauthorized access to browsing patterns and page content details.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable sophisticated reconnaissance attacks where adversaries gather intelligence about user browsing behavior, website structures, and potentially sensitive content access patterns. Attackers could leverage this vulnerability to reconstruct user navigation sequences, identify visited websites, and infer details about previously loaded pages without direct access to those resources. This type of information leakage could be particularly damaging in environments where users access confidential or sensitive information, as it provides attackers with indirect means of gathering intelligence about user activities and preferences.
Security professionals should note this vulnerability aligns with CWE-200, which covers "Information Exposure," and demonstrates how improper access control mechanisms can lead to unauthorized data disclosure. The flaw also relates to ATT&CK technique T1071.004, which involves application layer protocol usage for command and control communications, as the vulnerability could be exploited to gather intelligence that supports more sophisticated attack vectors. Organizations should prioritize updating to Firefox 48.0 or later versions to address this vulnerability, as the fix implemented by Mozilla properly restricts Resource Timing API access to only resources that are accessible to the current browsing context. Additionally, administrators should consider implementing network monitoring to detect anomalous API usage patterns that might indicate exploitation attempts, and security teams should review browser security configurations to ensure proper isolation of browsing contexts and resource access controls.