CVE-2026-92075 in Firefox
Summary
by MITRE • 09/15/2026
Mitigation bypass in the Networking component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security issue represents a critical failure within the networking subsystem of Mozilla Firefox, specifically characterized as a mitigation bypass rather than a direct code execution flaw or memory corruption error. In modern browser architectures, mitigations are defensive mechanisms designed to limit the impact of vulnerabilities that cannot be immediately patched or to restrict the capabilities available to an attacker who has achieved some level of initial access. These measures often include features like sandboxing, strict origin policies, and restrictions on low-level system interactions. A bypass in this context implies that an adversary was able to circumvent these protective layers, effectively nullifying their intended security guarantees. This type of vulnerability is particularly dangerous because it undermines the defense-in-depth strategy employed by browser developers, allowing potential exploits to operate with higher privileges or broader access than originally anticipated by the software design.
From a technical perspective, networking components handle all external communications for web content, including HTTP requests, WebSocket connections, and DNS resolutions. These modules are frequent targets for attackers seeking to perform cross-site request forgery, data exfiltration, or man-in-the-middle attacks. When mitigation mechanisms fail within this layer, it suggests that the boundary conditions between trusted browser processes and untrusted web content were not properly enforced. This could involve failures in enforcing same-origin policies, improper handling of network credentials, or weaknesses in how sandboxed tabs communicate with privileged parent processes. The existence of such a bypass indicates that while the core logic might have been secure against direct exploitation, the auxiliary protections meant to contain any potential breach were insufficiently robust or incorrectly configured for specific attack vectors.
The operational impact of this vulnerability is significant because it potentially allows malicious web pages or scripts to perform actions that should be restricted by browser security policies. An attacker could leverage this bypass to access sensitive user data stored in cookies, local storage, or session tokens across different domains if the origin policy enforcement was compromised. Furthermore, it may enable unauthorized network requests that mimic legitimate user behavior, facilitating account takeover attacks through cross-site request forgery scenarios where traditional CSRF protections are rendered ineffective by the mitigation failure. In severe cases, such a bypass could allow an attacker to intercept and modify traffic in ways that evade standard detection mechanisms, leading to data integrity issues or privacy violations for end-users browsing with affected versions of Firefox.
This vulnerability aligns closely with CWE-250, which describes execution under unintended control, as the mitigation failure allows code running in a restricted context to gain capabilities outside its intended scope. It also relates to CWE-941, concerning incorrect enforcement of communication flow restrictions, particularly if the bypass involves manipulating network requests between different security zones. In terms of offensive cybersecurity frameworks like MITRE ATT&CK, this flaw facilitates techniques associated with Collection and Exfiltration over C2 channels or Defense Evasion by allowing attackers to operate without triggering standard browser-based alerts that rely on these mitigations for detection. The ability to bypass sandboxing or policy enforcement is a key enabler for persistent access and lateral movement within a compromised user environment.
To address this risk, users must immediately update their Firefox installations to version 156 or the extended support release version 153.3, where these specific mitigation failures have been corrected by Mozilla engineers. Beyond updating software, organizations should enforce strict content security policies on internal web applications and ensure that third-party extensions are vetted for compliance with modern browser standards. Security teams should also monitor network logs for anomalous patterns of cross-origin requests or unusual data transmission volumes, which may indicate exploitation attempts targeting this class of vulnerability before patches can be deployed across all endpoints. Regular auditing of browser configurations and disabling unnecessary networking features in high-security environments further reduces the attack surface available to adversaries seeking to exploit such bypasses.