CVE-2021-23993

medium
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
5.5

Description

An attacker may perform a DoS attack to prevent a user from sending encrypted email to a correspondent. If an attacker creates a crafted OpenPGP key with a subkey that has an invalid self signature, and the Thunderbird user imports the crafted key, then Thunderbird may try to use the invalid subkey, but the RNP library rejects it from being used, causing encryption to fail. This vulnerability affects Thunderbird < 78.9.1.

Predictions

Exploit likelihood
20%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-23993

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-23993.html

OS impact

OSVersionStatusFixed in
arch archfixed78.9.1-1
suse slesaffected
debian debianbookwormfixed1:78.10.0-1
debian debianbullseyefixed1:78.10.0-1
debian debianforkyfixed1:78.10.0-1
debian debiansidfixed1:78.10.0-1
debian debiantrixiefixed1:78.10.0-1

References

Verify integrity in audit chain (admin only). AS-IS.