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 was fixed in 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
https://access.redhat.com/errata/RHSA-2026:6188
https://access.redhat.com/errata/RHSA-2026:6342
https://access.redhat.com/errata/RHSA-2026:6917
https://access.redhat.com/errata/RHSA-2026:8284
https://access.redhat.com/errata/RHSA-2026:8285
https://access.redhat.com/errata/RHSA-2026:8286
https://access.redhat.com/errata/RHSA-2026:8287
https://access.redhat.com/errata/RHSA-2026:8288
https://access.redhat.com/errata/RHSA-2026:8289
https://access.redhat.com/errata/RHSA-2026:8290
https://access.redhat.com/errata/RHSA-2026:8315
https://access.redhat.com/errata/RHSA-2026:8850
https://access.redhat.com/security/cve/CVE-2026-4371
https://bugzilla.redhat.com/show_bug.cgi?id=2451001
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4371.json

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 : 2026-07-15 02:22

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

CWE-130

Improper Handling of Length Parameter Inconsistency

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[{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-126"}]}, {"type": "Secondary", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "description": [{"lang": "en", "value": "CWE-130"}]}], "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 was fixed in 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": "2026-07-15T02:22:39.793", "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"}