CVE-2026-4371

A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9.

CVSS v3 7.4 HIGH

7.4^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://bugzilla.mozilla.org/show_bug.cgi?id=2023493	Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-23/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-24/	Vendor Advisory

Configurations

Configuration 1 (hide)

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

History

No history.

Information

Published : 2026-03-24 21:16

Updated : 2026-03-27 18:05

NVD link : CVE-2026-4371

Mitre link : CVE-2026-4371

CVE.ORG link : CVE-2026-4371

JSON object : View

Products Affected

mozilla

thunderbird

CWE

CWE-126

Buffer Over-read

{"id": "CVE-2026-4371", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.4, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.2, "exploitabilityScore": 2.2}]}, "published": "2026-03-24T21:16:29.583", "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2023493", "tags": ["Permissions Required"], "source": "security@mozilla.org"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "tags": ["Vendor Advisory"], "source": "security@mozilla.org"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/", "tags": ["Vendor Advisory"], "source": "security@mozilla.org"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-126"}]}], "descriptions": [{"lang": "en", "value": "A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability affects Thunderbird < 149 and Thunderbird < 140.9."}, {"lang": "es", "value": "Un servidor de correo malicioso podr\u00eda enviar cadenas malformadas con longitudes negativas, haciendo que el analizador lea memoria fuera del b\u00fafer. Si un servidor de correo o una conexi\u00f3n a un servidor de correo fueran comprometidos, un atacante podr\u00eda hacer que el analizador funcione mal, potencialmente bloqueando Thunderbird o filtrando datos sensibles. Esta vulnerabilidad afecta a Thunderbird < 149 y Thunderbird < 140.9."}], "lastModified": "2026-03-27T18:05:16.243", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*", "vulnerable": true, "matchCriteriaId": "4C0558B1-4113-45A8-8E37-A0793A67AD6D", "versionEndExcluding": "140.9.0"}, {"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*", "vulnerable": true, "matchCriteriaId": "40FE4697-89F1-46F6-8E28-41883647583B", "versionEndExcluding": "149.0"}], "operator": "OR"}]}], "sourceIdentifier": "security@mozilla.org"}