CVE-2006-4253 in Firefox
Summary
by MITRE
Concurrency vulnerability in Mozilla Firefox 1.5.0.6 and earlier allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via multiple Javascript timed events that load a deeply nested XML file, followed by redirecting the browser to another page, which leads to a concurrency failure that causes structures to be freed incorrectly, as demonstrated by (1) ffoxdie and (2) ffoxdie3. NOTE: it has been reported that Netscape 8.1 and K-Meleon 1.0.1 are also affected by ffoxdie. Mozilla confirmed to CVE that ffoxdie and ffoxdie3 trigger the same underlying vulnerability. NOTE: it was later reported that Firefox 2.0 RC2 and 1.5.0.7 are also affected.
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Analysis
by VulDB Data Team • 01/24/2025
This vulnerability represents a critical concurrency flaw in Mozilla Firefox versions 1.5.0.6 and earlier that demonstrates the dangerous intersection of memory management issues and JavaScript execution contexts. The flaw occurs when multiple JavaScript timed events are executed in rapid succession, specifically when these events load deeply nested XML files and subsequently redirect the browser to different pages. This sequence creates a race condition where the browser's internal structures become corrupted due to improper memory deallocation. The vulnerability operates at the core level of Firefox's JavaScript engine and DOM handling mechanisms, making it particularly dangerous as it can potentially be exploited to execute arbitrary code rather than simply causing a crash.
The technical implementation of this vulnerability involves a specific pattern of JavaScript execution that triggers memory corruption through improper handling of object references during concurrent operations. When the browser processes multiple timed JavaScript events that load XML content, it creates a scenario where memory structures allocated for XML parsing and DOM manipulation are simultaneously accessed and modified by competing threads. The redirect operation following XML loading exacerbates this issue by forcing the browser to switch contexts while memory cleanup operations are still in progress. This concurrency failure results in structures being freed incorrectly, leading to memory corruption that manifests as either immediate browser crashes or more sinister exploitation opportunities where attackers can manipulate memory contents to execute malicious code. The vulnerability is classified as a concurrency issue that aligns with CWE-362, which specifically addresses race conditions in software systems, and represents a classic example of improper resource management under concurrent access scenarios.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enabling remote code execution, making it a significant threat to user security. Attackers can leverage this vulnerability by crafting malicious web pages that contain the specific JavaScript patterns described in the exploit demonstrations ffoxdie and ffoxdie3. These exploits demonstrate how seemingly benign browser operations can be combined to create dangerous memory corruption conditions that bypass traditional security mechanisms. The fact that this vulnerability affects multiple browser versions including Firefox 2.0 RC2 and 1.5.0.7 indicates a fundamental flaw in the browser's memory management architecture that persisted across several releases, suggesting the issue was not adequately addressed in the initial patches. The vulnerability's exploitation requires no special privileges from the attacker and can be delivered through standard web browsing activities, making it particularly dangerous in real-world scenarios. From an ATT&CK perspective, this vulnerability maps to techniques involving process injection and memory corruption, specifically targeting the browser's JavaScript engine execution environment.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox versions to address the underlying concurrency issues in the JavaScript engine and DOM handling. Organizations should prioritize updating to Firefox 1.5.0.7 or later versions where Mozilla has implemented fixes for this specific memory management problem. Browser administrators should also consider implementing additional security measures such as disabling JavaScript execution in untrusted environments or using browser sandboxing technologies that can isolate potentially malicious code execution. The vulnerability highlights the importance of proper memory management in concurrent programming environments and underscores the need for thorough testing of race conditions in browser engines. Security monitoring should include detection of unusual JavaScript execution patterns that might indicate exploitation attempts, particularly those involving XML loading and rapid page redirection sequences. Given the potential for remote code execution, this vulnerability should be treated with high priority in security response protocols, and affected systems should be updated immediately to prevent exploitation. The incident also demonstrates the critical importance of maintaining up-to-date browser software and implementing layered security approaches that can protect against both known and emerging vulnerabilities in web browsers.