CVE-2026-100805 in Firefox
Summary
by MITRE • 09/29/2026
Race condition, use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 157.
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Analysis
by VulDB Data Team • 09/29/2026
The identified security flaw resides within the audio and video processing subsystem of Mozilla Firefox, specifically involving a race condition coupled with a use-after-free error. These types of vulnerabilities are among the most critical in modern software development because they exploit timing dependencies and memory management errors that can lead to arbitrary code execution or application crashes. The vulnerability was addressed in Firefox version 157, indicating that prior versions were susceptible to exploitation under specific conditions involving concurrent access to media resources.
A race condition occurs when multiple threads of execution access shared data concurrently without proper synchronization mechanisms. In the context of audio and video components, this typically involves operations such as decoding streams, managing buffers, or handling asynchronous events triggered by user interaction or network activity. When these operations are not properly serialized, one thread may attempt to read or modify memory that another thread is simultaneously freeing or reallocating. This lack of atomicity creates a window of opportunity where the application state becomes inconsistent and unpredictable.
The use-after-free aspect exacerbates the severity of this race condition by allowing an attacker who can trigger the specific timing sequence to access memory that has already been deallocated by the system. When memory is freed but still referenced, it may be reallocated for a different purpose before the original reference is cleared. If an attacker controls the data written into this newly allocated block, they can manipulate program execution flow. This mechanism is frequently leveraged in exploit chains to achieve arbitrary code execution on the victim's machine, potentially leading full system compromise depending on browser sandboxing effectiveness and other mitigating factors present in the operating environment.
From a classification perspective, this vulnerability aligns with CWE-362, which covers concurrent execution using shared resources with improper synchronization, and CWE-416, which addresses use after free errors. These categories highlight fundamental flaws in memory safety and thread management that are prevalent in complex multimedia processing engines where performance optimization often competes with strict correctness guarantees. The combination of these two weaknesses creates a potent attack vector that requires precise timing to exploit successfully but offers significant rewards for successful exploitation attempts.
The operational impact of this vulnerability is severe, particularly given the ubiquity of web-based media playback. Users who visit maliciously crafted websites containing specially designed audio or video content could trigger the race condition through normal browsing activities such as loading a page with embedded multimedia elements. Successful exploitation could result in remote code execution, allowing attackers to install malware, steal sensitive information like cookies and session tokens, or pivot into internal networks if browser isolation mechanisms are bypassed. Even without full compromise, the instability caused by memory corruption can lead to frequent crashes, degrading user experience and potentially causing denial of service conditions for legitimate users relying on media playback features.
Mitigation strategies primarily involve upgrading to Firefox version 157 or later, where these issues have been resolved through rigorous code review and patching efforts. Developers should ensure that all updates are applied promptly across organizational endpoints to minimize the window of exposure. For organizations deploying Firefox at scale, automated update policies should be enforced to guarantee that users benefit from security fixes without manual intervention. Additionally, enabling sandboxing features within the browser can limit the impact of any successful exploitation by restricting the privileges granted to renderer processes, thereby containing potential damage even if a vulnerability is triggered.
Security teams should also monitor for indicators of compromise related to memory corruption attacks, such as unusual process behavior or unexpected network connections originating from browser instances. While race conditions are difficult to detect through static analysis alone, dynamic testing and fuzzing techniques can help identify similar patterns in other components before they reach production environments. Continuous integration pipelines should include automated security checks that specifically target concurrency issues and memory safety violations to prevent regression of such critical flaws in future releases.