CVE-2026-109746 in Firefox
Summary
by MITRE • 10/13/2026
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 158.
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Analysis
by VulDB Data Team • 10/13/2026
The identified vulnerability represents a critical failure within Mozilla Firefox's Document Object Model implementation, specifically concerning the enforcement of security components designed to isolate content and prevent unauthorized access between different execution contexts. In web browser architecture, the DOM serves as the primary interface for scripts to interact with page structure and data, making it a frequent target for exploitation attempts aimed at bypassing same-origin policies or sandbox boundaries. The specific flaw described indicates that under certain conditions, an attacker could manipulate DOM operations in a manner that circumvents expected security checks, effectively allowing malicious code to access resources or perform actions that should have been restricted by the browser's internal safeguards. This type of vulnerability is particularly dangerous because it undermines the fundamental trust model upon which modern web applications rely, potentially leading to unauthorized data exfiltration, session hijacking, or further lateral movement within a victim's environment if combined with other attack vectors such as cross-site scripting.
From a technical perspective, this issue likely stems from an inconsistency in how Firefox validates permissions and context boundaries during DOM manipulation events. Security components typically rely on strict checks to ensure that scripts originating from one origin cannot interfere with or read data from another without explicit permission. When these checks are bypassed through crafted DOM interactions, the isolation between tabs, frames, or extensions is compromised. This aligns closely with CWE-200, which classifies information exposure vulnerabilities where an attacker gains access to sensitive system or application information that was not intended for them. Furthermore, this behavior maps directly to MITRE ATT&CK technique T1537, specifically the sub-technique of communication through browser extensions if the bypass involves extension APIs, or more broadly to privilege escalation within the context of a single user session. The ability to bypass these controls allows an adversary to escalate their privileges from a low-level sandboxed environment to one with higher access rights, facilitating data theft or persistence mechanisms that would otherwise be blocked by standard security protocols.
The operational impact of this vulnerability is significant for any organization relying on Firefox as its primary web browser, particularly in environments where users interact with untrusted websites or handle sensitive corporate information online. An attacker could exploit this flaw to steal cookies, local storage data, or credentials stored within the browser session without triggering standard security alerts. In enterprise settings, this could lead to credential theft and subsequent account compromise if multi-factor authentication is not strictly enforced at the application level rather than relying solely on browser-based protections. Additionally, because DOM vulnerabilities often require user interaction such as clicking a malicious link or visiting a compromised webpage, they serve as effective entry points for drive-by download attacks or phishing campaigns that aim to establish initial access within an organization's network perimeter. The severity is further amplified by the fact that browsers are ubiquitous and frequently used for accessing critical business applications, making them high-value targets for threat actors seeking broad impact with minimal effort.
To mitigate this risk, organizations must ensure that all instances of Firefox are updated to version 158 or later, as indicated in the vendor's advisory. This update contains the necessary patches to correct the logic errors within the DOM security components and restore proper enforcement of isolation boundaries. In addition to immediate patching, it is advisable for administrators to implement application control policies that restrict the execution of unsigned scripts where possible and enforce strict content security policies across web applications hosted internally or accessed externally. Users should be educated on recognizing suspicious links and avoiding interaction with untrusted sites until patches are deployed. Regular vulnerability scanning and monitoring for indicators of compromise related to browser exploitation can also help detect potential attempts to leverage this flaw before significant damage occurs. Maintaining a robust patch management process is essential, as delays in applying vendor fixes leave systems exposed to known exploits that are increasingly common in the current threat landscape.