CVE-2026-16365 in Firefox
Summary
by MITRE • 07/21/2026
Privilege escalation in the DOM: Workers component. This vulnerability was fixed in Firefox 153.
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Analysis
by VulDB Data Team • 07/21/2026
This privilege escalation vulnerability exists within the Document Object Model workers component of Firefox browsers, representing a critical security flaw that allows attackers to elevate their privileges beyond normal browser sandbox boundaries. The issue specifically affects how the browser handles worker threads and their interaction with the DOM, creating potential pathways for malicious code to gain elevated system access. Such vulnerabilities typically arise from insufficient validation of cross-origin communication between main threads and worker contexts, where improper privilege checks fail to prevent unauthorized access to sensitive browser APIs.
The technical flaw stems from inadequate sandboxing mechanisms within Firefox's implementation of web workers, which are designed to run JavaScript in background threads separate from the main execution thread. When workers interact with DOM elements or attempt to access privileged browser functions, the system should enforce strict security boundaries based on origin policies and privilege levels. However, this vulnerability demonstrates a failure in these protective measures, allowing malicious actors to exploit race conditions or improper access controls during worker initialization or communication phases. The flaw particularly impacts how Firefox handles cross-origin worker contexts where proper privilege separation fails to maintain isolation between different security domains.
The operational impact of this privilege escalation vulnerability extends beyond typical browser-based attacks to potentially enable full system compromise when combined with other exploitation techniques. Attackers could leverage this weakness to execute arbitrary code with elevated privileges, access sensitive user data, perform unauthorized network operations, or even gain access to the underlying operating system resources. The vulnerability affects users across all supported platforms where Firefox is deployed, making it particularly dangerous as a mass exploit vector. Security researchers have noted that such privilege escalation flaws often serve as initial access points for more sophisticated attacks, potentially leading to complete system compromise when combined with other zero-day exploits.
Mitigation strategies should focus on immediate patch application to Firefox version 153 or later, which contains the necessary security fixes addressing the worker privilege escalation issue. Organizations should also implement network monitoring to detect suspicious worker behavior patterns and consider browser hardening measures such as disabling unnecessary worker functionality in restricted environments. The vulnerability aligns with common weakness enumerations identified under CWE-284 for improper access control and CWE-352 for cross-site request forgery, while mapping to ATT&CK techniques involving privilege escalation and persistence mechanisms. Security teams must also conduct thorough testing of web applications that rely heavily on worker threads to ensure proper isolation boundaries are maintained and that no additional attack vectors exist within their browser-based applications or services.