What’s Vulnerable › Vulnerabilities

CVE-2025-3875: Sender Spoofing via Malformed From Header in Thunderbird

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-14 · updated 2026-06-17
• Weakness: CWE-290

Description

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; from 129.0 before 138.0.1 — fixed in 128.10.0, 138.0.1

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 128.10.0, 138.0.1. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1950629
• https://www.mozilla.org/security/advisories/mfsa2025-34/
• https://www.mozilla.org/security/advisories/mfsa2025-35/
• https://lists.debian.org/debian-lts-announce/2025/05/msg00022.html

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