CVE-2015-4478 in Firefox
Summary
by MITRE
Mozilla Firefox before 40.0 and Firefox ESR 38.x before 38.2 do not impose certain ECMAScript 6 requirements on JavaScript object properties, which allows remote attackers to bypass the Same Origin Policy via the reviver parameter to the JSON.parse method.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability identified as CVE-2015-4478 represents a critical security flaw in Mozilla Firefox versions prior to 40.0 and Firefox ESR 38.x versions prior to 38.2. This issue stems from the browser's incomplete implementation of ECMAScript 6 standards, specifically concerning JavaScript object property handling within the JSON.parse method. The flaw allows malicious actors to exploit the absence of proper validation mechanisms that should enforce certain ECMAScript 6 requirements, creating a pathway for bypassing fundamental web security measures.
The technical root cause of this vulnerability lies in Firefox's insufficient enforcement of ECMAScript 6 specifications when processing the reviver parameter within the JSON.parse function. According to the ECMAScript 6 standard, the reviver parameter should undergo specific validation to prevent unauthorized access to object properties that could otherwise be exploited. The browser's failure to properly validate this parameter creates an opportunity for attackers to manipulate JavaScript object properties in ways that circumvent the Same Origin Policy, a fundamental security mechanism that prevents scripts from one origin from accessing resources from another origin.
This vulnerability directly impacts the browser's security model by allowing remote attackers to execute cross-origin information disclosure attacks. When an attacker crafts malicious JSON content with a specially designed reviver parameter, they can potentially access object properties that should normally be restricted based on origin policies. The attack vector typically involves loading malicious content through a web page that executes JSON.parse with an attacker-controlled reviver function, enabling unauthorized data access across different origins. The implications extend beyond simple information disclosure, as this weakness could potentially enable more sophisticated attacks that leverage the bypassed security controls.
The operational impact of CVE-2015-4478 is significant for organizations relying on Firefox browsers, as it exposes users to potential data breaches and cross-site scripting attacks. This vulnerability aligns with CWE-124, which describes "Buffer Underflow," and can be categorized under ATT&CK technique T1059.007 for JavaScript execution. The flaw particularly affects web applications that depend on JSON parsing for data exchange between different origins, as it undermines the security boundaries that should protect against unauthorized access to sensitive information. Organizations may experience compromised user data, unauthorized access to web services, and potential escalation of privileges through the exploitation of this bypass mechanism.
Mitigation strategies for this vulnerability primarily involve updating Firefox browsers to versions 40.0 or later for regular releases, and 38.2 or later for ESR releases. Security administrators should also implement additional protective measures such as content security policies, regular security audits of web applications, and monitoring for suspicious JSON parsing activities. The fix implemented by Mozilla addresses the core issue by properly enforcing ECMAScript 6 requirements for the reviver parameter, ensuring that object property access adheres to the Same Origin Policy restrictions. Organizations should also consider implementing web application firewalls and network monitoring solutions to detect potential exploitation attempts targeting this specific vulnerability.