Vulnerability · NVD

CVE-2026-4371

CVE-2026-4371, high severity (CVSS 7.4): 1 tracked app concerned, all fixed or indeterminable on their current version.

Severity (CVSS): 7.4
Exploitation: 0.6 %
Tracked apps: 1
Still exposed: 0

Published on 2026-03-24

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.

Attack vector : Network No privileges required No user interaction

Show raw CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H

EPSS 0.64% exploit very unlikely percentile 48.5%

Tracked apps referencing this CVE

For each app: the affected range, the fixing version, and where the tracked app stands today.

Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected <140.9.0 Fixed in 140.9.0 Latest tracked 156.0.1 patched

Observed affected builds (100)

140.0.1 140.0 139.0.2 139.0.1 139.0 138.0.2 138.0.1 138.0 137.0.2 137.0.1 137.0 136.0.1 136.0 115.14.0 115.13.0 115.12.2 115.12.1 115.11.1 115.11.0 115.10.2 115.10.1 115.10.0 115.9.0 115.8.1 115.8.0 115.7.0 115.6.1 115.6.0 115.5.2 115.5.1 +70 · see history

Vulnerable CPE configurations (2)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<140.9.0	cpe:2.3:a:mozilla:thunderbird:::::esr:::*
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<149.0	cpe:2.3:a:mozilla:thunderbird:::::-:::*

View on NVD ↗ Advisory · www.mozilla.org

Manage your fleet with Appaloosa

Appaloosa pushes OS updates, apps and policies to your Windows, macOS, iOS and Android devices from one console.

Discover Appaloosa MDM