CVE-2026-84136 in Firefox
Summary
by MITRE • 09/01/2026
Other issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155 and Firefox ESR 153.2.
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Analysis
by VulDB Data Team • 09/01/2026
The identified security flaw resides within the navigation component of Mozilla's Document Object Model implementation, specifically affecting how user interface elements are rendered and interacted with during web page processing. This issue highlights a deficiency in the internal handling of DOM structures that manage browser chrome or complex navigational interfaces embedded within web content. Such vulnerabilities typically arise when the engine fails to properly validate input data before integrating it into the active document tree, leading to potential inconsistencies in how state changes are propagated across interface layers. The vulnerability was addressed and resolved in Firefox version 155 as well as the extended support release branch at version 153.2, indicating that the patching process involved rigorous testing of navigation states to ensure stability and security integrity before deployment to end users.
From a technical perspective, flaws within DOM manipulation components often stem from improper memory management or logic errors in how event listeners are attached or detached during dynamic updates. When an attacker can influence the structure or content of the navigation component through crafted web pages, they may exploit these inconsistencies to trigger unintended behaviors such as cross-site scripting vectors, denial of service conditions via resource exhaustion, or potentially more severe outcomes like arbitrary code execution if memory corruption is involved. The specific nature of this issue suggests that the vulnerability likely allowed for unexpected state transitions or data leakage within the navigation context, which could be leveraged by malicious actors to bypass security controls designed to isolate web content from browser internals.
The operational impact of such vulnerabilities varies depending on the exploitability and the sensitivity of the affected component. In many cases, DOM-related issues in navigation modules can lead to information disclosure where sensitive data accessible through the interface is exposed to untrusted scripts. Alternatively, if the flaw allows for control flow hijacking or memory corruption, it could result in remote code execution with the privileges of the browser process. This poses a significant risk as browsers operate with elevated permissions relative to standard applications, making any compromise particularly dangerous for user privacy and system security. Users relying on Firefox for sensitive activities such as online banking or corporate communications are directly impacted until they update their software to include these critical fixes.
Mitigation strategies primarily involve ensuring that all instances of the browser are updated to the patched versions mentioned above. For organizations deploying Firefox across enterprise environments, it is advisable to verify patch compliance through automated vulnerability management tools and enforce strict content security policies to limit the capabilities of scripts running within web pages. Additionally, developers should adhere to secure coding practices when interacting with DOM elements, ensuring that all inputs are sanitized and validated before being processed by navigation components. Regular updates remain the most effective defense against such vulnerabilities as they incorporate upstream fixes from Mozilla's development team who continuously monitor and address emerging threats in their rendering engine.
This incident aligns with common vulnerability classifications found in industry standards such as CWE-79, which covers cross-site scripting flaws often associated with improper DOM manipulation, or potentially CWE-120 if memory buffer issues are involved depending on the underlying cause. In terms of attack tactics, this type of flaw could be leveraged within MITRE ATT&CK techniques related to client-side evasion or initial access through malicious web content. By addressing these vulnerabilities promptly and maintaining up-to-date software configurations, organizations can significantly reduce their exposure to exploitation attempts targeting browser-based interfaces. Continuous monitoring for new advisories from Mozilla is essential to stay ahead of potential zero-day exploits that may target unpatched versions before widespread adoption occurs in the user base.