CVE-2026-109756 in Firefox
Summary
by MITRE • 10/13/2026
Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
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Analysis
by VulDB Data Team • 10/13/2026
The identified vulnerability represents a critical flaw within the Document Object Model implementation of Mozilla Firefox, specifically affecting the navigation component responsible for handling browser history and page transitions. As a privilege escalation issue, this defect allows an attacker to bypass intended security restrictions by manipulating how the DOM processes navigational events or state changes. In typical web application architectures, the DOM serves as the bridge between HTML content and JavaScript execution contexts, enforcing strict boundaries between different origins to prevent unauthorized access to sensitive data or functionality. When these boundaries are compromised through a flaw in the navigation logic, scripts operating under lower privilege levels can potentially execute actions or access resources that should be restricted to higher-privileged contexts or other domains.
The technical root of this vulnerability likely stems from improper validation or state management within the internal mechanisms that track browsing history and page loads. During complex navigational sequences, such as those involving iframes, cross-origin redirects, or dynamic content updates, the browser may fail to correctly isolate the execution context or misinterpret the origin of a request. This oversight enables an attacker who controls malicious web content to exploit race conditions or logic errors in how the navigation component processes state transitions. By carefully crafting specific sequences of DOM manipulations and navigational triggers, an adversary can trick the browser into granting elevated permissions to their script, effectively breaking out of the sandbox environment that protects user data from untrusted websites.
The operational impact of this vulnerability is severe due to its potential for cross-site scripting-like effects without requiring traditional injection vectors. An attacker could leverage this flaw to steal sensitive cookies, session tokens, or local storage data belonging to other sites visited by the same browser instance. Furthermore, privilege escalation in the DOM can facilitate further attacks such as clickjacking, where an attacker overlays invisible elements on top of legitimate UI components to trick users into performing unintended actions like transferring funds or changing account settings. The ability to escalate privileges within the browsing context undermines the fundamental trust model of web browsers, potentially leading to full system compromise if combined with other exploits that target browser plugins or extensions running with higher permissions than standard tabs.
Mitigation for this vulnerability was implemented in Firefox version 158 and Firefox Extended Support Release (ESR) version 153.5 through rigorous code reviews and enhanced validation checks within the navigation module. These updates likely involve stricter origin checking, improved isolation of navigational states, and more robust handling of edge cases during DOM manipulation events. Users are strongly advised to update their browsers immediately to patch this security hole. Additionally, developers should adhere to strict Content Security Policy (CSP) configurations to limit the impact of any potential future exploits by restricting script execution sources. Industry standards such as CWE-269, which covers Improper Privilege Management, and ATT&CK technique T1053, associated with Scheduled Task or Job manipulation for persistence and privilege escalation, provide frameworks for understanding how such flaws are categorized and mitigated in broader security architectures. Regular auditing of DOM usage patterns and minimizing the use of dangerous APIs like eval() or innerHTML without proper sanitization remain essential practices to prevent similar vulnerabilities from being introduced into web applications.