CVE-2011-2993 in Firefox
Summary
by MITRE
The implementation of digital signatures for JAR files in Mozilla Firefox 4.x through 5, SeaMonkey 2.x before 2.3, and possibly other products does not prevent calls from unsigned JavaScript code to signed code, which allows remote attackers to bypass the Same Origin Policy and gain privileges via a crafted web site, a different vulnerability than CVE-2008-2801.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability described in CVE-2011-2993 represents a critical security flaw in the digital signature implementation for JAR files within Mozilla Firefox versions 4.x through 5 and SeaMonkey 2.x before 2.3. This issue stems from a fundamental weakness in how these browsers handle the isolation between signed and unsigned JavaScript code, creating a pathway for malicious actors to circumvent security mechanisms that should otherwise protect users from untrusted content. The flaw specifically targets the Same Origin Policy enforcement mechanism, which is a cornerstone of web security that prevents scripts from one origin from accessing resources of another origin without proper authorization. The vulnerability allows for privilege escalation through crafted web content that can manipulate the execution flow between signed and unsigned code components.
The technical implementation flaw lies in the browser's failure to properly enforce code isolation when processing JAR files that contain digital signatures. When a JAR file is signed, the browser should create a clear boundary between the signed code that can be trusted and the unsigned code that cannot. However, the vulnerability allows unsigned JavaScript code to make direct calls to signed code within the JAR file, effectively breaking the security boundary that should protect against cross-origin access. This occurs because the signature verification process does not adequately prevent the execution context switching that would normally be restricted when unsigned code attempts to interact with signed components. The flaw operates at the application layer and leverages the browser's JavaScript engine to execute malicious code sequences that can manipulate the security context of the running application.
The operational impact of this vulnerability is severe as it enables remote attackers to bypass essential web security controls from malicious websites. An attacker could craft a web page that loads a specially constructed JAR file containing both signed and unsigned JavaScript components, then use the unsigned code to make calls to the signed components that would normally be restricted. This privilege escalation allows the attacker to perform actions that should be limited to trusted code, including accessing sensitive data, making network requests, or executing arbitrary code within the browser's security context. The vulnerability is particularly dangerous because it operates silently in the background, allowing attackers to exploit the trust relationship between signed components and the browser without user awareness or intervention.
This vulnerability aligns with CWE-284, which describes inadequate access control mechanisms, and maps to ATT&CK technique T1059.007 for JavaScript execution. The flaw demonstrates a classic case of insufficient privilege separation in security-critical code components. Organizations should immediately update to patched versions of Firefox and SeaMonkey, as the vulnerability affects multiple browser versions and could be exploited in the wild. Additional mitigations include implementing strict content security policies, disabling JAR file processing in web environments, and monitoring for suspicious JavaScript behavior that attempts to access signed code components. The vulnerability highlights the importance of maintaining proper code isolation boundaries and demonstrates how digital signature implementations must account for all possible code interaction patterns to prevent security bypasses. Security teams should also consider implementing network-based protections such as web application firewalls that can detect and block malicious JAR file loading attempts.