CVE-2026-16407 in Firefox
Summary
by MITRE • 07/21/2026
Mitigation bypass in the DOM: Service Workers component. This vulnerability was fixed in Firefox 153.
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Analysis
by VulDB Data Team • 07/21/2026
This vulnerability represents a significant security flaw in Firefox's implementation of service workers within the Document Object Model architecture, specifically affecting the browser's ability to properly isolate and manage background processes that operate independently of web pages. The issue stems from an inadequate mitigation mechanism that fails to properly enforce security boundaries between different execution contexts, allowing potentially malicious code to bypass intended protection measures. Service workers function as proxy servers that run in the background to handle network requests, push notifications, and caching operations while maintaining a persistent presence even when the user closes the browser tab. The vulnerability manifests when these components fail to properly validate or restrict access to sensitive APIs and resources, creating potential attack vectors for privilege escalation or information disclosure attacks. This flaw particularly impacts Firefox versions prior to 153 where the underlying security controls were insufficient to prevent unauthorized access patterns that should have been blocked by the browser's security model.
The technical implementation flaw involves a failure in the service worker registration and execution pipeline where the browser does not adequately verify the origin or permissions of code attempting to interact with protected resources. This bypass occurs at the DOM level where service workers are initialized and managed, allowing attackers to exploit race conditions or improper access control checks that should have prevented unauthorized cross-origin operations. The vulnerability can be categorized under CWE-284 as an improper access control issue within the browser's security framework, specifically affecting the privileged execution environment of service worker processes. When exploited, this flaw enables attackers to perform operations that should require specific permissions or authentication, potentially allowing them to read sensitive data, modify resources, or execute arbitrary code with elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally undermines the security model that service workers are designed to maintain. Service workers are intended to operate in a sandboxed environment while providing powerful capabilities for offline functionality and background processing, but this bypass allows attackers to circumvent these protective measures. The attack surface includes potential data exfiltration scenarios where malicious code could access cached resources or intercept network traffic that should remain protected. Additionally, the vulnerability may enable more sophisticated attacks such as cross-site request forgery manipulation or the creation of persistent backdoors through service worker registration that can survive browser sessions. This represents a critical weakness in Firefox's security architecture that affects all web applications relying on service workers for enhanced functionality. The impact is particularly concerning given that service workers are increasingly used for modern web applications that require offline capabilities, push notifications, and background processing.
Mitigation strategies for this vulnerability require immediate deployment of Firefox version 153 or later where the underlying security controls have been properly implemented to address the access control bypass issue. Organizations should conduct comprehensive security assessments of their web applications to identify any service worker implementations that may be vulnerable to exploitation, particularly those handling sensitive user data or requiring elevated privileges. The recommended approach involves implementing proper service worker registration validation and ensuring that all code interactions with these components are properly authenticated and authorized. Security teams should monitor for potential exploitation attempts through network traffic analysis and browser console monitoring to detect any unauthorized access patterns that may indicate successful exploitation of this vulnerability. Additionally, developers should review their service worker implementations to ensure they follow security best practices such as proper origin validation, secure caching mechanisms, and appropriate use of encryption for sensitive data handling. This vulnerability highlights the importance of continuous security testing and validation of browser security features, particularly those that operate in background processes where traditional user interface security measures may not apply. The fix implemented in Firefox 153 addresses the core issue by strengthening the access control checks within the service worker component while maintaining compatibility with legitimate web application functionality.