CVE-2026-92020 in Firefox
Summary
by MITRE • 09/15/2026
Privilege escalation due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security issue resides within the Graphics subsystem of Mozilla Firefox, specifically targeting the WebRender component which is responsible for hardware-accelerated rendering of web content using WebGL and other graphics APIs. This vulnerability represents a critical failure in boundary condition handling during memory management operations associated with graphical resource allocation or buffer manipulation. In complex rendering pipelines, precise calculation of array indices, buffer sizes, and stride values is essential to prevent out-of-bounds access. When these boundaries are not strictly enforced due to logical errors or insufficient validation checks, the application may read from or write to memory locations outside the intended scope. This type of flaw typically stems from a lack of rigorous input sanitization regarding dimensions provided by web content or internal state variables that track resource limits. The consequence is an incorrect boundary condition error which allows for unauthorized access to adjacent memory structures, potentially leading to arbitrary code execution with elevated privileges if exploited in conjunction with other techniques such as heap spraying or type confusion attacks.
From a technical perspective, this vulnerability aligns closely with Common Weakness Enumeration categories related to improper restriction of operations within the bounds of a resource boundary. Specifically it reflects weaknesses where software does not properly enforce limits on actions performed by an actor regarding memory access patterns. The WebRender engine operates at a low level close to the graphics driver interface and relies heavily on efficient data structures for texture management, shader compilation, and frame buffer composition. A lapse in validating these boundaries can allow maliciously crafted web content or compromised extensions to trigger unintended behavior within the browser process. This could result in information disclosure where sensitive data stored in adjacent memory blocks is leaked to an attacker-controlled context. More severely it enables privilege escalation scenarios where a sandboxed renderer process might escape its isolation constraints by exploiting the flawed boundary checks to gain control over higher-privileged processes or system resources. Such escapes undermine the fundamental security model of modern browsers which depend on strict compartmentalization between different execution contexts.
The operational impact of this vulnerability is significant as it affects multiple major release channels including stable Firefox versions and extended support releases indicating a widespread exposure across diverse user bases. Attackers could potentially craft specific web pages or malicious scripts that trigger these boundary condition failures during rendering operations such as canvas drawing WebGL context manipulation or CSS layout calculations involving complex graphics layers. Successful exploitation would allow an attacker to execute arbitrary code within the browser process with the same privileges as the current user effectively bypassing sandbox protections designed to limit damage from compromised websites. This poses a severe risk to users who visit untrusted sites download malicious extensions or interact with dynamically generated content that exploits these rendering flaws. The availability of fixes in Firefox 156 and various ESR branches highlights the urgency for organizations relying on older versions to update promptly as legacy deployments remain vulnerable until patched.
Mitigation strategies primarily involve applying the vendor-provided patches released in the specified version updates which address the underlying logic errors responsible for the boundary miscalculations. Administrators should ensure that all endpoints running Firefox are updated to at least Firefox 156 or the corresponding ESR versions mentioned including Firefox ESR 115.41 Firefox ESR 140.16 and Firefox ESR 153.3. In environments where immediate patching is not feasible temporary mitigations might include disabling WebGL functionality through browser configuration policies restricting access to potentially dangerous web APIs or employing network-level filtering solutions that block known malicious domains attempting to deliver exploit code. Additionally enabling strict content security policies within deployed applications can help reduce the attack surface by limiting how scripts interact with graphics contexts and resource boundaries. Continuous monitoring for anomalous behavior in system logs related to memory allocation failures or unexpected process terminations may also aid in detecting attempted exploitation activities before full compromise occurs maintaining overall infrastructure resilience against this class of rendering-based vulnerabilities.