CVE-2026-4729

Description

Memory safety bugs present in Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

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:*:*:*:*:-:*:*:* - VULNERABLE

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

Mozilla Firefox < 149

Mozilla Thunderbird < 149

PoC / Exploit Code

⚠ For Security Research Only

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

python

<!--
  PoC Template for Memory Corruption Vulnerability
  This is a generic example to trigger potential browser crashes.
  Target: CVE-2026-4729 (Firefox < 149)
-->
<html>
<body>
<script>
  // Attempt to trigger memory corruption through heap spraying or specific object manipulation
  try {
    var buffer = new ArrayBuffer(0x100000);
    var view = new Uint8Array(buffer);
    // Filling memory to potentially corrupt adjacent objects
    for (var i = 0; i < view.length; i++) {
      view[i] = 0x41;
    }
    // Triggering the vulnerability logic would require specific vulnerability details
    console.log("PoC executed. If browser crashes, vulnerability might be present.");
  } catch (e) {
    console.log("Error executing PoC: " + e.message);
  }
</script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-4729
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-4729
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-4729/
[4] VulDB https://vuldb.com/cve/CVE-2026-4729
[5] https://bugzilla.mozilla.org/buglist.cgi?bug_id=1944033%2C1997282%2C2009213%2C2011412%2C2021925%2C2022034
[6] https://www.mozilla.org/security/advisories/mfsa2026-20/
[7] https://www.mozilla.org/security/advisories/mfsa2026-23/

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-4729", "sourceIdentifier": "[email protected]", "published": "2026-03-24T13:16:08.830", "lastModified": "2026-04-13T15:17:45.597", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Memory safety bugs present in Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149 and Thunderbird 149."}, {"lang": "es", "value": "Errores de seguridad de memoria presentes en Firefox 148 y Thunderbird 148. Algunos de estos errores mostraron evidencia de corrupción de memoria y presumimos que con suficiente esfuerzo algunos de estos podrían haber sido explotados para ejecutar código arbitrario. Esta vulnerabilidad afecta a Firefox < 149 y Thunderbird < 149."}], "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: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": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-120"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "40FE4697-89F1-46F6-8E28-41883647583B"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=1944033%2C1997282%2C2009213%2C2011412%2C2021925%2C2022034", "source": "[email protected]", "tags": ["Broken Link"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}