CVE-2026-4371

Estado: ModificadaAlta (7.4)—

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

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H
Puntuación base: 7.4

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.64%
Percentil entre todas las CVEs puntuadas: 49
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access75 %
Impacto principalT1005 Data from Local Systemcollection80 %
Impacto secundarioT1499.004 Application or System Exploitationimpact70 %

Red sin privilegios (AV:N/PR:N), pero requiere servidor comprometido. Parser de correo lee memoria fuera de buffer: fuga de datos sensibles (T1005) y DoS por crash (T1499.004). CWE-126 confirma lectura fuera de límites.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network Traffic Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Application Isolation and Sandboxing

Tecnologías afectadas (1)

Mozilla — Thunderbird

CWE

CWE-126
CWE-130

Referencias

JSON original (NVD)

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      "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."
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      "lang": "es",
      "value": "Un servidor de correo malicioso podría enviar cadenas malformadas con longitudes negativas, haciendo que el analizador lea memoria fuera del búfer. Si un servidor de correo o una conexión a un servidor de correo fueran comprometidos, un atacante podría hacer que el analizador funcione mal, potencialmente bloqueando Thunderbird o filtrando datos sensibles. Esta vulnerabilidad afecta a Thunderbird &lt; 149 y Thunderbird &lt; 140.9."
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  "lastModified": "2026-07-15T02:22:39.793",
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