A security issue was found in Thunderbird before version 78.9.1. If a Thunderbird user has previously imported Alice's OpenPGP key, and Alice has extended the validity period of her key, but Alice's updated key has not yet been imported, an attacker may send an email containing a crafted version of Alice's key with an invalid subkey, Thunderbird might subsequently attempt to use the invalid subkey, and will fail to send encrypted email to Alice.
A security issue was found in Thunderbird before version 78.9.1. If a Thunderbird user has previously imported Alice's OpenPGP key, and Alice has extended the validity period of her key, but Alice's updated key has not yet been imported, an attacker may send an email containing a crafted version of Alice's key with an invalid subkey, Thunderbird might subsequently attempt to use the invalid subkey, and will fail to send encrypted email to Alice.
https://www.mozilla.org/en-US/security/advisories/mfsa2021-13/#CVE-2021-23991 https://bugzilla.mozilla.org/show_bug.cgi?id=1673240
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