Undefined behavior in the WebRTC: Signaling 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
<!--
PoC Concept for CVE-2026-4718
This script demonstrates a basic WebRTC setup that may trigger
undefined behavior in vulnerable versions of Firefox/Thunderbird.
Replace the signaling logic with specific malicious payloads
based on the bug report analysis.
-->
<!DOCTYPE html>
<html>
<head>
<title>CVE-2026-4718 PoC</title>
</head>
<body>
<h1>WebRTC Signaling Vulnerability Test</h1>
<script>
// Create a PeerConnection to trigger signaling component
const pc = new RTCPeerConnection({
iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
});
// Create a data channel to stimulate activity
const dataChannel = pc.createDataChannel('chat');
// Create an offer to generate SDP (Signaling Data)
pc.createOffer().then(offer => {
// In a real exploit, malformed SDP or signaling messages
// would be crafted here to hit the undefined behavior.
console.log('Generated Offer:', offer.sdp);
return pc.setLocalDescription(offer);
}).then(() => {
console.log('Local description set.');
}).catch(error => {
console.error('Error during WebRTC setup:', error);
});
// Log any unexpected behavior or crashes
window.addEventListener('error', (e) => {
console.log('Caught error:', e.message);
});
</script>
</body>
</html>