CVE-2026-92050 in Firefox
Summary
by MITRE • 09/15/2026
Sandbox escape due to race condition in the XPConnect component. This vulnerability was fixed in Firefox 156.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw resides within the XPConnect subsystem of Mozilla Firefox, a critical bridge that facilitates communication between JavaScript code running in web content and native C++ components on the host system. As a race condition-based sandbox escape, this vulnerability exploits timing discrepancies during object property access or method invocation across different execution contexts. Specifically, the issue arises when concurrent threads attempt to interact with XPConnect-managed objects without proper synchronization mechanisms being enforced at every step of the interaction lifecycle. This lack of atomicity allows an attacker-controlled script to manipulate internal state variables in a way that bypasses expected security checks, effectively breaking out of the restricted browser sandbox environment where web content is typically confined.
From a technical perspective, race conditions are particularly insidious because they rely on precise timing and concurrency control failures within the underlying C++ implementation. In this scenario, an attacker could craft malicious JavaScript code designed to trigger multiple simultaneous requests or state changes against XPConnect interfaces. By carefully orchestrating these operations, it is possible for one thread to read a value while another thread modifies it in between, leading to inconsistent object states that violate security assumptions made by the browser's isolation mechanisms. This inconsistency can be leveraged to execute arbitrary code with higher privileges than those granted to standard web content, potentially allowing full control over the user’s system depending on the execution context and available exploit primitives.
The operational impact of such a vulnerability is severe, as it directly compromises the fundamental security model of modern browsers which relies heavily on sandboxing to prevent malicious websites from affecting the host operating system. Successful exploitation could lead to remote code execution, data exfiltration, or further lateral movement within an enterprise network if users are compelled to visit compromised sites. The ability to escape the browser sandbox removes a primary layer of defense against drive-by download attacks and other web-based threats that previously relied on containment strategies rather than strict isolation.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-362, which describes concurrent execution using shared resources with improper synchronization. Furthermore, in the context of the MITRE ATT&CK framework, this type of exploit falls under techniques related to privilege escalation and sandbox escape, specifically mapping to tactics that involve bypassing application security restrictions or exploiting software vulnerabilities for initial access and persistence. The fix implemented in Firefox version 156 addresses these concurrency issues by introducing stricter locking mechanisms and ensuring atomic operations during critical sections of XPConnect processing, thereby eliminating the window of opportunity for race condition exploitation.
To mitigate risks associated with similar vulnerabilities, developers must prioritize rigorous thread safety analysis when implementing cross-language bindings or inter-process communication layers within browser engines. Implementing comprehensive unit tests that specifically target concurrency scenarios can help identify timing-dependent flaws before deployment. Additionally, adopting static code analysis tools focused on detecting data races and employing dynamic instrumentation during testing phases provides additional visibility into potential synchronization errors. For end-users, maintaining up-to-date software versions remains the most effective defense against such exploits, as vendors typically release patches promptly after validating fixes for critical security issues like this one.