CVE-2015-4492 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the XMLHttpRequest::Open implementation in Mozilla Firefox before 40.0 and Firefox ESR 38.x before 38.2 might allow remote attackers to execute arbitrary code via a SharedWorker object that makes recursive calls to the open method of an XMLHttpRequest object.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/22/2024
The vulnerability described in CVE-2015-4492 represents a critical use-after-free flaw within Mozilla Firefox's implementation of XMLHttpRequest::Open functionality. This security issue affects Firefox versions prior to 40.0 and Firefox ESR 38.x versions prior to 38.2, creating a significant attack surface that could be exploited by remote adversaries. The vulnerability specifically manifests when a SharedWorker object executes recursive calls to the open method of an XMLHttpRequest object, leading to memory corruption that adversaries can potentially leverage for arbitrary code execution. The flaw stems from improper memory management where freed memory locations are accessed after being deallocated, a pattern that aligns with common software security vulnerabilities classified under CWE-416.
The technical implementation of this vulnerability involves the interaction between SharedWorker objects and XMLHttpRequest functionality within Firefox's JavaScript engine. When a SharedWorker makes recursive calls to XMLHttpRequest::Open, the memory allocation and deallocation patterns become inconsistent, creating a window where freed memory can be accessed by subsequent operations. This particular scenario exploits the complex interaction between Firefox's multi-threaded worker architecture and its XMLHttpRequest implementation, where the garbage collector and memory management systems fail to properly track object references during recursive operations. The vulnerability is particularly dangerous because it can be triggered through web content without requiring any user interaction, making it a prime target for drive-by attacks and automated exploitation campaigns.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a complete compromise of the affected system's security model. Remote attackers who successfully exploit this flaw can gain full control over the victim's browser environment, potentially leading to data theft, session hijacking, or further lateral movement within the network. The vulnerability's exploitation requires no special privileges or user interaction beyond visiting a malicious website, making it particularly dangerous in enterprise environments where users may encounter untrusted web content. Security researchers have noted that this vulnerability fits within the ATT&CK framework under the T1059.007 technique for "Command and Scripting Interpreter: JavaScript" and potentially T1078.004 for "Valid Accounts: Default Accounts" if the exploited browser has elevated privileges.
Mitigation strategies for CVE-2015-4492 primarily focus on immediate patching and system hardening measures. Organizations should prioritize updating Firefox installations to versions 40.0 or later for regular releases, and 38.2 or later for ESR versions, as these releases contain the necessary memory management fixes. Browser security configurations should be reviewed to disable unnecessary JavaScript features and implement strict content security policies that limit the execution of potentially malicious code. Network-level protections such as web application firewalls and intrusion detection systems can help detect exploitation attempts, while security monitoring should be enhanced to identify unusual browser behavior patterns that may indicate exploitation. The vulnerability demonstrates the critical importance of proper memory management in web browser implementations and serves as a reminder of the need for continuous security testing and vulnerability assessment in complex software systems. Organizations should also consider implementing browser sandboxing and privilege separation techniques to limit the potential impact of successful exploitation attempts.