CVE-2025-3875: Mozilla Thunderbird

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid From address to be used. For example, if the From header contains an (invalid) value "Spoofed Name ", Thunderbird treats spoofed@example.com as the actual address. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

Affected products

• Mozilla Thunderbird: before 128.10.0 (fixed in 128.10.0); from 129.0, before 138.0.1 (fixed in 138.0.1)

Published 2025-05-14. Last modified 2026-06-17.