CVE-2026-74946 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, and Firefox ESR 153.1.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/18/2026
The identified security flaw resides within the CanvasWebGL component of Mozilla Firefox, specifically involving incorrect boundary conditions that facilitate privilege escalation. This vulnerability highlights a critical failure in input validation and memory management logic during the rendering process for WebGL contexts. When an application or webpage utilizes HTML5 canvas elements with WebGL acceleration to render complex graphics, the browser must carefully manage how data is passed between JavaScript code and the underlying GPU drivers via OpenGL or Vulkan interfaces. The defect arises when specific boundary checks are either missing, incorrectly implemented, or bypassed due to edge cases in array indexing or buffer allocation logic. This allows a maliciously crafted web page to write beyond allocated memory boundaries or execute operations with elevated privileges that should be restricted by the browser's sandboxing mechanisms.
From a technical perspective, this type of vulnerability is often categorized under CWE-120 Buffer Overflow if it involves writing past the end of a buffer, or more broadly under CWE-787 Out-of-bounds Write when dealing with memory corruption issues in C++ codebases like Gecko. The root cause typically stems from insufficient validation of array indices or size parameters before they are used to calculate memory addresses for GPU command buffers. In WebGL implementations, data is often uploaded to the graphics card via mapped memory regions. If boundary conditions are not strictly enforced, an attacker can manipulate these mappings to overwrite adjacent memory structures, potentially including function pointers, return addresses, or security-critical metadata within the browser process. This corruption enables the execution of arbitrary code with the same privileges as the user running the browser, effectively breaking out of the web content sandbox.
The operational impact of this vulnerability is severe due to its potential for remote exploitation via standard web browsing activities. An attacker can host a malicious website containing specially crafted WebGL shaders and JavaScript that triggers the boundary condition error when rendered in an affected version of Firefox. Upon visiting such a site, particularly on systems where hardware acceleration is enabled, the browser may crash or, more dangerously, allow the execution of arbitrary code. This leads to full system compromise if the user has administrative privileges, as the attacker gains control over the process context. The risk is exacerbated by the fact that WebGL is widely supported and often used for legitimate purposes such as gaming, data visualization, and 3D modeling, making it difficult for users or administrators to disable without impacting functionality.
Mitigation strategies primarily rely on timely software updates. Users must upgrade to Firefox version 154, Firefox ESR 115.39, Firefox ESR 140.14, or Firefox ESR 153.1, where the boundary checks in the CanvasWebGL component have been corrected and validated against known exploit patterns. For organizations managing large fleets of devices, automated patch management systems should be configured to prioritize this update due to its high severity rating associated with remote code execution capabilities. Additionally, security teams can implement browser hardening policies that restrict WebGL access for untrusted domains or disable hardware acceleration entirely if the specific use case does not require it, thereby reducing the attack surface until all endpoints are fully patched. Monitoring network traffic for unusual outbound connections from Firefox processes may also help detect active exploitation attempts in real-time environments where immediate patching is delayed.
This vulnerability aligns with MITRE ATT&CK technique T1203 Exploitation for Client Execution, as it involves leveraging a client-side application flaw to execute malicious code on the victim's machine. It also relates to T1059 Command and Scripting Interpreter if the initial execution leads to further scripting activities within the compromised context. The fix emphasizes the importance of rigorous static analysis and fuzz testing in graphics stack development, particularly for components that interface directly with low-level system resources like GPU drivers. Continuous integration pipelines should include specific test cases targeting WebGL boundary conditions to prevent regression errors similar to this one from reaching production builds in future releases.