CVE-2011-4688 in Firefox
Summary
by MITRE
Mozilla Firefox 8.0.1 and earlier does not prevent capture of data about the times of Same Origin Policy violations during IFRAME loading attempts, which makes it easier for remote attackers to determine whether a document exists in the browser cache via crafted JavaScript code.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability described in CVE-2011-4688 represents a sophisticated information disclosure issue within Mozilla Firefox versions 8.0.1 and earlier. This flaw exploits the browser's handling of Same Origin Policy violations during iframe loading operations, creating a covert channel that adversaries can leverage to infer cache state information. The vulnerability stems from Firefox's inadequate suppression of timing data associated with cross-origin policy enforcement mechanisms, specifically during the loading sequence of iframe elements that attempt to access resources from different origins.
The technical mechanism behind this vulnerability involves the browser's timing mechanisms that track when Same Origin Policy violations occur during iframe loading attempts. When a web page attempts to load content from a different origin within an iframe, Firefox records timing information about these violations, including the duration between various stages of the loading process. This timing data inadvertently reveals whether the requested resource exists in the browser's cache, as cached resources typically load faster than network resources due to reduced latency. Attackers can craft JavaScript code to measure these timing differences and deduce cache state information without direct access to the cached content itself.
This vulnerability creates significant operational impact by enabling remote attackers to perform cache poisoning attacks and fingerprint browser behavior patterns. The ability to determine cache state information opens pathways for more sophisticated attacks including cache deception techniques where adversaries can manipulate browser behavior based on inferred cache states. From a security perspective, this represents a violation of the principle of least information disclosure, where the browser inadvertently leaks timing information that should remain hidden to maintain security boundaries. The vulnerability specifically relates to CWE-200, which addresses improper exposure of sensitive information, and can be categorized under ATT&CK technique T1566 for credential access through cache poisoning methods.
The exploitation of this vulnerability requires minimal privileges and can be executed through standard web page content, making it particularly dangerous in phishing campaigns and targeted attacks. Attackers can use this information to build more effective social engineering campaigns by understanding which resources are cached in target browsers, potentially enabling them to craft more convincing deceptive content. The vulnerability also impacts privacy preservation mechanisms since it allows external parties to infer browsing behavior patterns based on cache state information. Mitigation strategies should focus on implementing proper timing obfuscation techniques and ensuring that timing information related to Same Origin Policy violations is not exposed to JavaScript contexts. Browser vendors should consider implementing consistent timing delays for cross-origin resource loading operations regardless of cache state to prevent timing-based information leakage.