Security Vulnerability Report
中文
CVE-2026-6754 CVSS 7.5 HIGH

CVE-2026-6754

Published: 2026-04-21 13:16:21
Last Modified: 2026-04-22 14:53:49

Description

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

CVSS Details

CVSS Score
7.5
Severity
HIGH
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* - VULNERABLE
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* - VULNERABLE
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* - VULNERABLE
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* - VULNERABLE
Firefox < 150
Firefox ESR < 115.35
Firefox ESR < 140.10
Thunderbird < 150
Thunderbird < 140.10

PoC / Exploit Code

⚠ For Security Research Only
The following code is for security research and authorized testing only.
python
// Conceptual PoC for Use-after-Free in JavaScript Engine // Triggering a UAF scenario let obj = []; // Step 1: Allocate object for (let i = 0; i < 100; i++) { obj.push({a: i}); } // Step 2: Trigger vulnerability (Free object) // Hypothetical function that frees the object but keeps a reference trigger_vulnerability(obj[50]); // Step 3: Reallocate memory with attacker-controlled data // Fill the freed memory slot let crafted_data = new Uint32Array(100); for (let i = 0; i < crafted_data.length; i++) { crafted_data[i] = 0x41414141; // 'AAAA' } // Step 4: Access the freed pointer (Crash or Exploit) print(obj[50].a); // Accessing freed memory

References

Raw JSON Data

JSON
{"cve": {"id": "CVE-2026-6754", "sourceIdentifier": "[email protected]", "published": "2026-04-21T13:16:21.420", "lastModified": "2026-04-22T14:53:48.573", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10."}], "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:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "115.35.0", "matchCriteriaId": "E69D71F5-CAAA-4F28-AB9F-9F898A52D506"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "150.0", "matchCriteriaId": "67B01D49-66FA-4C76-9EB4-2B8CD61FBEB2"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionStartIncluding": "140.0", "versionEndExcluding": "140.10.0", "matchCriteriaId": "528443E0-C15A-4E70-9187-8E1BAAE84A42"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.10.0", "matchCriteriaId": "48217E2F-FFD3-4385-B962-15365B293DA7"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2027541", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-30/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-31/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-32/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-33/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-34/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}