CVE-2026-16356 in Firefox
Summary
by MITRE • 07/21/2026
Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox 153, Firefox ESR 115.38, and Firefox ESR 140.13.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability under discussion represents a critical sandbox escape flaw within the Disability Access APIs component of Mozilla Firefox browsers. This security issue stems from improper memory management practices that create opportunities for malicious actors to bypass browser sandboxing mechanisms. The use-after-free condition occurs when the application continues to reference memory locations that have already been freed, potentially allowing attackers to manipulate memory contents and execute arbitrary code outside the intended restricted environment.
The technical exploitation of this vulnerability leverages the fundamental weakness in how Firefox handles accessibility API interactions within its security boundaries. When the browser processes disability access functionality, specific memory allocation patterns create conditions where freed memory blocks can be reallocated and manipulated by attacker-controlled data. This particular flaw exists within the component responsible for providing accessibility features to users with disabilities, making it an attractive target for exploitation as it runs with elevated privileges relative to normal browsing operations.
The operational impact of this vulnerability extends beyond simple privilege escalation, as successful exploitation could enable attackers to completely circumvent Firefox's security model. The sandbox escape capability allows malicious code to access system resources that should remain isolated from web content execution, potentially leading to full system compromise. This represents a significant threat to user privacy and system integrity since the accessibility APIs are designed to provide legitimate assistance while maintaining strict security boundaries.
Security researchers have identified this vulnerability as aligning with CWE-416, which specifically addresses use-after-free conditions in software implementations. The flaw demonstrates poor memory management practices that violate fundamental security principles established in secure coding standards and best practices. From an adversary perspective, this vulnerability maps to several ATT&CK techniques including privilege escalation and sandbox evasion, making it particularly dangerous for targeted attacks against browser environments.
Mitigation strategies should focus on immediate patch deployment across all affected Firefox versions including the recently released Firefox 153, Firefox ESR 115.38, and Firefox ESR 140.13. Organizations should prioritize updating their browser installations to prevent exploitation attempts while implementing additional monitoring for suspicious access patterns within accessibility API components. The fix implemented by Mozilla addresses the underlying memory management issue through proper deallocation handling and validation checks that prevent reuse of freed memory blocks, thereby eliminating the attack surface that previously enabled sandbox escape conditions.
Additional defensive measures include implementing strict browser security policies that limit accessibility API exposure to trusted applications only, while also monitoring for unusual API call patterns that might indicate exploitation attempts. System administrators should consider deploying automated patch management solutions to ensure timely updates across all browser installations within their environments. The vulnerability serves as a reminder of the critical importance of proper memory management in security-sensitive components and highlights the need for comprehensive code review processes focused on identifying use-after-free conditions in complex software systems.