CVE-2026-16351 in Firefox
Summary
by MITRE • 07/21/2026
Sandbox escape due to use-after-free in the DOM: Navigation 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
This vulnerability represents a critical sandbox escape flaw originating from a use-after-free condition within the Document Object Model navigation component of the firefox browser. The issue stems from improper memory management where freed memory locations are still being accessed or referenced by subsequent operations, creating a potential pathway for malicious code execution beyond the intended browser sandbox boundaries. Such vulnerabilities are particularly dangerous as they can allow attackers to bypass security restrictions that normally isolate web content from the underlying operating system and other applications.
The technical implementation of this flaw occurs within the dom navigation component which handles browser navigation operations including page transitions, history management, and url processing. When a malicious webpage triggers specific navigation sequences combined with memory allocation patterns that result in freed memory being reallocated for different purposes, an attacker can manipulate the execution flow to execute arbitrary code with elevated privileges. This particular use-after-free vulnerability is categorized under common weakness enumeration cwes 416 which specifically addresses use after free conditions where software continues to reference memory after it has been freed.
The operational impact of this vulnerability extends beyond typical web browser exploitation as it fundamentally compromises the security model that separates trusted browser components from untrusted web content. Attackers can leverage this flaw to escape the sandbox environment and potentially gain access to system resources, file systems, or execute arbitrary commands on the host machine. The vulnerability affects multiple firefox versions including the standard release 153 and extended support releases 115.38 and 140.13, indicating it was present across several security maintenance channels and required coordinated patching efforts.
From a threat modeling perspective, this vulnerability aligns with attack techniques described in the mitre att&ck framework under initial access and privilege escalation categories. The exploitation typically involves crafting malicious web content that triggers specific browser navigation patterns to create the use-after-free condition, followed by memory corruption techniques to redirect execution flow. Security professionals should note that such sandbox escape vulnerabilities often require complex exploitation chains involving multiple primitive vulnerabilities or memory corruption techniques to achieve successful compromise.
The remediation approach for this vulnerability focuses on proper memory management practices and ensuring that all object references are properly invalidated after deallocation. Browser vendors have implemented various mitigations including heap randomization, address space layout randomization, and enhanced memory safety checks within the dom navigation component. Additionally, the patch addresses fundamental memory handling patterns that could lead to use-after-free conditions during navigation operations and ensures proper reference counting mechanisms are maintained throughout the lifecycle of dom objects. Organizations should prioritize immediate deployment of the patched firefox versions to protect against exploitation attempts targeting this specific vulnerability class.
This vulnerability demonstrates the ongoing challenges in maintaining secure browser implementations where complex interaction between multiple components can create unexpected security boundaries. The fix represents a comprehensive approach to memory safety that addresses not just the immediate issue but also strengthens the overall security posture of the browser's navigation subsystem. Security researchers and penetration testers should understand that use-after-free vulnerabilities in core browser components pose significant risks due to their potential for privilege escalation and sandbox bypass capabilities, making them high-priority targets for both defensive measures and exploit development activities.