CVE-2019-11746 in Firefox
Summary
by MITRE
A use-after-free vulnerability can occur while manipulating video elements if the body is freed while still in use. This results in a potentially exploitable crash. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2019-11746 represents a critical use-after-free condition that manifests within Mozilla's browser and email client software ecosystems. This flaw occurs during the manipulation of video elements when the underlying memory structure becomes prematurely freed while still being referenced or accessed by active processes. The technical nature of this vulnerability places it squarely within the domain of memory safety issues that can lead to arbitrary code execution when exploited by malicious actors. The affected software versions span multiple product lines including Firefox browser, Thunderbird email client, and their respective extended support releases, indicating a widespread impact across Mozilla's software portfolio.
The underlying technical mechanism of this vulnerability stems from improper memory management during video element processing within the browser's rendering engine. When video elements are dynamically manipulated or removed from the document object model, the associated memory structures may be deallocated before all references to them are properly cleared or released. This creates a scenario where subsequent operations attempting to access the freed memory location can result in unpredictable behavior including crashes or potential exploitation. The vulnerability specifically affects versions where the garbage collection and memory management systems fail to properly track references to video element objects during their lifecycle transitions, creating a window where memory corruption can occur.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable remote code execution attacks against affected systems. When exploited successfully, the use-after-free condition can allow attackers to inject malicious code into the browser process, potentially leading to complete system compromise. The vulnerability's exploitation requires careful crafting of video content that triggers the specific memory management race condition, making it a sophisticated attack vector that would likely be targeted in advanced persistent threat campaigns. Organizations running affected versions of Mozilla software face significant risk as these applications are commonly used for web browsing and email processing, making them attractive targets for cybercriminals seeking to establish persistent access to networks.
Mitigation strategies for this vulnerability require immediate deployment of patched software versions across all affected systems. Mozilla released updates for Firefox version 69 and Thunderbird versions 68.1, 60.9, and their respective extended support releases to address the memory management flaw. Security administrators should prioritize patching these applications as a high-priority task, particularly in environments where users regularly access untrusted web content or email. Additional defensive measures include implementing browser hardening configurations, enabling sandboxing features, and deploying network-based intrusion detection systems to monitor for exploitation attempts. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software development, and represents a classic example of how memory safety issues can translate into severe security risks in modern web browsers. Organizations should also consider implementing application whitelisting controls and monitoring for suspicious memory access patterns that could indicate exploitation attempts.