CVE-2026-4717

Description

Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CVSS Details

CVSS Score

9.8

Severity

CRITICAL

CVSS Vector

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

Configurations (Affected Products)

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

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

Firefox < 149

Firefox ESR < 140.9

Thunderbird < 149

Thunderbird < 140.9

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!--
PoC for CVE-2026-4717 (Conceptual)
This script attempts to trigger the Netmonitor component vulnerability.
-->
<!DOCTYPE html>
<html>
<head>
    <title>CVE-2026-4717 PoC</title>
</head>
<body>
<script>
    // Attempt to interact with Netmonitor internals to trigger privilege escalation
    try {
        // Hypothetical trigger for the Netmonitor vulnerability
        var exploitPayload = {
            action: "monitor_debug",
            params: {
                force_privilege: true,
                target: "system_root"
            }
        };
        
        // Simulate sending a malicious network request pattern
        fetch('data:text/json,' + JSON.stringify(exploitPayload))
            .then(response => console.log("Payload triggered"))
            .catch(error => console.log("Exploit attempt failed", error));
            
        console.log("CVE-2026-4717: Checking for Netmonitor vulnerability...");
    } catch(e) {
        console.log("Error during PoC execution: " + e.message);
    }
</script>
<p>If the browser is vulnerable, it may crash or execute code.</p>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-4717
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-4717
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-4717/
[4] VulDB https://vuldb.com/cve/CVE-2026-4717
[5] https://bugzilla.mozilla.org/show_bug.cgi?id=2021695
[6] https://www.mozilla.org/security/advisories/mfsa2026-20/
[7] https://www.mozilla.org/security/advisories/mfsa2026-22/
[8] https://www.mozilla.org/security/advisories/mfsa2026-23/
[9] https://www.mozilla.org/security/advisories/mfsa2026-24/

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-4717", "sourceIdentifier": "[email protected]", "published": "2026-03-24T13:16:07.600", "lastModified": "2026-04-13T15:17:43.440", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}, {"lang": "es", "value": "Escalada de privilegios en el componente Netmonitor. Esta vulnerabilidad afecta a Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, y Thunderbird < 140.9."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.9.0", "matchCriteriaId": "DA62D95E-CB01-4586-83DB-5094116FC939"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2021695", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-22/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/", "source": "[email protected]"}]}}