CVE-2026-92048 in Firefox
Summary
by MITRE • 09/15/2026
Sandbox escape due to incorrect boundary conditions in the Widget: Win32 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 vulnerability represents a critical security flaw within the Mozilla Gecko rendering engine, specifically affecting the Widget subsystem for Windows operating systems. As a sandbox escape vector, this issue allows malicious content executed within the browser's restricted environment to break out into the host system with elevated privileges. The root cause lies in incorrect boundary condition handling during memory operations or data validation routines associated with Win32 API interactions. In complex software architectures like Firefox, the widget layer serves as an abstraction between the cross-platform Gecko engine and native operating system interfaces. When these boundaries are not strictly enforced, particularly regarding input size limits or array indexing, it creates opportunities for buffer overflows or out-of-bounds reads that can be exploited to corrupt memory structures in a way that facilitates arbitrary code execution outside the sandbox.
From a technical perspective, this flaw likely involves improper validation of user-controlled data before it is passed to underlying Windows APIs. The Win32 component handles graphical elements such as windows, buttons, and scrollbars, requiring frequent communication with the operating system's kernel. If an attacker can craft specific inputs that trigger these boundary condition failures, they may overwrite critical memory locations or manipulate control flow pointers. This type of vulnerability is particularly dangerous because it undermines one of the primary defense-in-depth strategies employed by modern web browsers: sandboxing. By escaping this isolation layer, a malicious actor gains direct access to the user's file system, network stack, and other sensitive resources without requiring additional privilege escalation exploits against the operating system itself.
The operational impact of such a vulnerability is severe, potentially leading to full compromise of the end-user device. An attacker could use this sandbox escape to install persistent malware, exfiltrate confidential data stored on the local machine, or pivot into internal network segments if the browser has access to them. Given that Firefox is widely used in enterprise environments and by individuals handling sensitive information, the availability of an exploit for this flaw poses a significant risk to confidentiality, integrity, and availability. The fact that it was resolved in recent updates indicates that active exploitation may have been observed or detected through rigorous internal testing prior to public disclosure.
To mitigate risks associated with similar vulnerabilities, organizations should ensure that all instances of Firefox are updated to version 156 for standard releases or version 153.3 for Extended Support Release channels immediately. Beyond patching, implementing application whitelisting and strict network segmentation can limit the blast radius if a sandbox escape occurs. Security teams should also monitor for indicators of compromise related to unusual process creation events originating from browser processes, as this is often a hallmark of successful exploitation attempts. Continuous monitoring and adherence to secure coding practices that emphasize rigorous input validation are essential defenses against boundary condition flaws in complex software systems.
This vulnerability aligns with Common Weakness Enumeration categories such as CWE-120 Buffer Copy without Checking Size of Input Classic Buffer Overflow or CWE-787 Out-of-bounds Write, depending on the specific memory corruption mechanism exploited. In terms of tactical classification under MITRE ATT&CK, this falls under T1055 Process Injection or potentially T1068 Exploitation for Privilege Escalation if the escape leads to higher system rights. Understanding these mappings helps security professionals prioritize remediation efforts and align their detection strategies with known adversary behaviors associated with browser-based attacks.