CVE-2021-23991
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…
Does this matter?
Lower severity and a low EPSS score (1.03%). Track it; it rarely justifies an emergency change on its own.
Description
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. This vulnerability affects Thunderbird < 78.9.1.
- CVSS 3.1
- 6.8 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- EPSS
- 1.03% probability · 64th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- mozilla/thunderbird
- Source
- security@mozilla.org
EPSS 1.0% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1673240Exploit, Issue Tracking, Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-13/Release Notes, Vendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1673240Exploit, Issue Tracking, Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2021-13/Release Notes, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.