CVE-2025-26696: Crafted email message incorrectly shown as being encrypted

Severity: high (CVSS 7.0 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: 2025-03-10 · updated 2026-06-17
Weakness: CWE-290

Description

Certain crafted MIME email messages that claimed to contain an encrypted OpenPGP message, which instead contained an OpenPGP signed message, were wrongly shown as being encrypted. This vulnerability was fixed in Thunderbird 136 and Thunderbird 128.8.

Affected products

Mozilla Thunderbird: before 128.8.0; from 129.0 before 136.0 — fixed in 128.8.0, 136.0

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 128.8.0, 136.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1864205
https://www.mozilla.org/security/advisories/mfsa2025-17/
https://www.mozilla.org/security/advisories/mfsa2025-18/

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