CVE-2020-12398

Name: CVE-2020-12398
Creator: NVD / NIST
Published: 2020-07-09T15:15:10.677+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.98%

Last modified Jun 17, 2026

CVE-2020-12398 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 0.98% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Probability

0.98%

57.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-319

Affected Software

Vendor	Product	Versions
Mozilla	Thunderbird	< 68.9.0
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	19.10
Canonical	Ubuntu Linux	20.04

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1613623Issue Tracking, Permissions Required, Vendor Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-22/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1613623Issue Tracking, Permissions Required, Vendor Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-22/Vendor Advisory

Timeline

Published: Jul 9, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-12398?

How severe is CVE-2020-12398?

CVE-2020-12398 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.98% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12398?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-12398?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST