CVE-2016-5287 in Firefox
Summary
by MITRE
A potentially exploitable use-after-free crash during actor destruction with service workers. This issue does not affect releases earlier than Firefox 49. This vulnerability affects Firefox < 49.0.2.
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Analysis
by VulDB Data Team • 09/28/2022
The vulnerability identified as CVE-2016-5287 represents a critical use-after-free condition that occurs during the destruction process of actor objects within Firefox's service worker implementation. This flaw specifically manifests when the browser's rendering engine attempts to clean up actor resources while service workers are active, creating a scenario where memory previously allocated to actor objects may be accessed after being freed. The issue resides in Firefox's handling of asynchronous operations between the main thread and service worker contexts, where improper resource management leads to memory corruption that can be exploited by malicious actors.
The technical nature of this vulnerability aligns with CWE-416, which describes the use of freed memory condition where a program continues to reference memory that has already been deallocated. This particular implementation flaw occurs in the browser's inter-process communication mechanism, where actor objects serve as communication channels between different browser processes. When service workers execute and subsequently terminate, the actor destruction sequence fails to properly synchronize the cleanup process, leaving references to freed memory accessible to subsequent operations. The vulnerability is particularly dangerous because it occurs during the natural termination process of web applications, making it difficult to detect and exploit through conventional means.
The operational impact of CVE-2016-5287 extends beyond simple application crashes to potentially enable remote code execution on affected systems. Attackers can leverage this use-after-free condition by crafting malicious web content that triggers the specific sequence of events leading to memory corruption. The vulnerability affects Firefox versions prior to 49.0.2, making it particularly relevant for organizations that have not updated their browser installations. The exploitation process typically involves creating a service worker that manipulates actor objects in a way that causes the browser to free memory while still maintaining references to it. This creates a predictable memory layout that can be leveraged for arbitrary code execution through techniques such as return-oriented programming or heap spraying.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox installations to version 49.0.2 or later, where Mozilla has implemented proper synchronization mechanisms during actor destruction. Organizations should also consider implementing browser hardening measures such as enabling sandboxing, restricting service worker capabilities, and deploying web application firewalls that can detect and block malicious service worker implementations. The vulnerability demonstrates the importance of proper resource management in complex browser architectures and highlights the need for comprehensive testing of asynchronous communication patterns. Security teams should monitor for indicators of compromise related to this vulnerability through network traffic analysis and endpoint detection systems that can identify exploitation attempts targeting the specific memory corruption patterns associated with use-after-free conditions in browser environments.