CVE-2026-92064 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-based systems. As a sandbox escape vector, this issue allows malicious content executed within the browser's restricted environment to break out into the host operating system with elevated privileges. The root cause lies in incorrect boundary conditions during memory management or input validation processes within the Win32 component of the widget architecture. In complex software like web browsers, components such as widgets handle user interface elements and interact heavily with native OS APIs. When these interactions involve dynamic data from untrusted sources, such as content loaded via JavaScript or HTML5 features, strict boundary checks are essential to prevent buffer overflows, out-of-bounds reads, or writes that could corrupt memory structures used by the sandboxing mechanism.
The technical nature of this flaw suggests a failure in validating input lengths or array indices before they are passed to underlying Windows API calls. If an attacker can craft specific web content that triggers these boundary condition errors, it may lead to arbitrary code execution outside the browser's security container. This is particularly dangerous because modern browsers rely on sandboxing to isolate potentially malicious scripts from sensitive system resources and user data. By exploiting incorrect boundary checks, a threat actor could bypass protections like Windows Defender Application Control or other endpoint detection mechanisms that depend on process isolation. The vulnerability likely involves improper handling of widget state transitions or event handlers where the size of input buffers is not correctly verified against allocated memory limits, leading to heap corruption or stack overflow scenarios that can be leveraged for control flow hijacking.
The operational impact of this sandbox escape is severe, as it effectively neutralizes one of the primary defense layers in web browsing security. Successful exploitation could allow an attacker to execute arbitrary code on the victim's machine with the same privileges as the browser process. This typically means full system compromise if the user runs the browser with standard administrative rights or if additional privilege escalation vulnerabilities are chained together. The attack vector is primarily remote, requiring only that a user visits a maliciously crafted website or opens a compromised document rendered by Firefox. Given the widespread use of Firefox and its ESR variants in enterprise environments, this vulnerability poses a significant risk to organizational security postures. Attackers could deploy malware, exfiltrate sensitive data stored locally, install persistent backdoors, or pivot further into internal networks depending on the network configuration and user permissions.
Mitigation strategies must prioritize immediate patching as outlined by the vendor's release notes. Users should upgrade to Firefox version 156 or Firefox Extended Support Release (ESR) version 153.3 without delay to ensure that the corrected boundary checks are in place within the Win32 widget component. For enterprise environments, IT administrators should enforce automatic update policies through group policy objects or endpoint management solutions like Microsoft Endpoint Manager to guarantee timely deployment of these fixes across all workstations. Additionally, organizations can implement application whitelisting and strict code signing requirements to limit the execution of unsigned binaries, thereby reducing the impact even if a sandbox escape occurs. Network-level controls such as web filtering proxies should also be configured to block access to known malicious domains that might host exploit kits targeting this specific vulnerability in older browser versions still present on some legacy systems.
From an industry standard perspective, this flaw aligns with CWE-120 Buffer Copy without Checking Size of Input and potentially CWE-787 Out-of-bounds Write depending on the exact memory corruption mechanism observed during exploitation attempts. In terms of adversary tactics, it maps to MITRE ATT&CK technique T1059 Command and Scripting Interpreter if used for initial execution within the sandbox, followed by T1068 Exploitation for Privilege Escalation as the attacker moves from the browser process to the operating system level. Understanding these mappings helps security teams categorize the risk accurately and prioritize remediation efforts based on established threat intelligence frameworks. Continuous monitoring of endpoint detection and response systems for anomalous behavior, such as unexpected child processes spawned by firefox.exe or unusual network connections initiated immediately after browsing activity, can provide early warning indicators of exploitation attempts in environments where patching cannot be applied instantly.