CVE-2020-12398

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-07-09 · updated 2026-06-17
Weakness: CWE-319

Description

If Thunderbird is configured to use STARTTLS for an IMAP server, and the server sends a PREAUTH response, then Thunderbird will continue with an unencrypted connection, causing email data to be sent without protection. This vulnerability affects Thunderbird < 68.9.0.

Affected products

Canonical Ubuntu Linux: 16.04, 18.04, 19.10, 20.04
Mozilla Thunderbird: before 68.9.0 — fixed in 68.9.0

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 68.9.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1613623
https://usn.ubuntu.com/4421-1/
https://www.mozilla.org/security/advisories/mfsa2020-22/
https://bugzilla.mozilla.org/show_bug.cgi?id=1613623
https://usn.ubuntu.com/4421-1/
https://www.mozilla.org/security/advisories/mfsa2020-22/

Get alerted when CVE-2020-12398 or the next vulnerability affects your stack