What’s Vulnerable › Vulnerabilities

CVE-2026-3889: Spoofing issue in Thunderbird

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-24 · updated 2026-06-17
• Weakness: CWE-451

Description

Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.

Affected products

• Mozilla Thunderbird: before 140.9.0; before 149.0 — fixed in 140.9.0, 149.0

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 140.9.0, 149.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2020723
• https://www.mozilla.org/security/advisories/mfsa2026-23/
• https://www.mozilla.org/security/advisories/mfsa2026-24/

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