CVE-2021-23991: mozilla thunderbird
Vulnerability summary
CVE-2021-23991 is a medium (CVSS 6.8) vulnerability in mozilla thunderbird. EPSS estimates a 1.03% chance of exploitation in the next 30 days, higher than 63.3% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 12 · Related 5Timeline
- 24-06-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
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 metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated6.8MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated6.8MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS trend
Probability
1.03%
Chance of exploitation in the next 30 days
Percentile
63%
Versus all other CVEs
30-day change
0.00 pp
From 1.03% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundExploit Reference (bugzilla.mozilla.org)
Maturity: unknown
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Debian1 product
- thunderbird< 1:78.10.0-1
Mozilla1 product
- thunderbird≥ unspecified, < 78.9.1 | < 78.9.1
Ubuntu1 product
- thunderbird< 1:78.11.0+build1-0ubuntu0.18.04.2 | < 1:78.11.0+build1-0ubuntu0.20.04.2
3 vendors · 3 products
