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Fencer Vulns
high 7.5

CVE-2020-12398 json

If Thunderbird is configured to use STARTTLS for an IMAP server, and the server sends a PREAUTH response, then Thunderbird will continue wi…

published 2020-07-09 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4710

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Thunderbird 68.9.0
  • thunderbird Debian 14, Debian 13, Debian 12 1:68.9.0-1

debian advisories DEBIAN-CVE-2020-12398

  • thunderbird Ubuntu 16.04 LTS 1:68.10.0+build1-0ubuntu0.16.04.1
  • thunderbird Ubuntu 18.04 LTS 1:68.10.0+build1-0ubuntu0.18.04.1
  • thunderbird Ubuntu 20.04 LTS 1:68.10.0+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-12398

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird RHEL 7 68.9.0-1.el7_8
  • thunderbird RHEL 8 68.9.0-1.el8_2
  • thunderbird RHEL 6 68.9.0-1.el6_10
  • thunderbird RHEL 8.1 EUS 68.9.0-1.el8_1
  • thunderbird RHEL 8.0 E4S 68.9.0-1.el8_0

red hat advisories RHSA-2020:2611RHSA-2020:2615RHSA-2020:2614RHSA-2020:2613RHSA-2020:2616

  • MozillaThunderbird SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1 68.9.0-3.85.2

suse advisories SUSE-SU-2020:1591-2SUSE-SU-2020:1591-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.1 68.9.0-lp151.2.41.1

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2020:0799-1

  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 68.9.0-r0

alpine advisories ALPINE-CVE-2020-12398

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird Arch Linux 68.9.0-1

arch linux advisories AVG-1179

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12398 updated cvss 7.5

Mozilla: Security downgrade with IMAP STARTTLS leads to information leakage

  • Red Hat Enterprise Linux 5 thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) thunderbird 68.9.0-1.el8_2
    fixed: vendor fix RHSA-2020:2614
  • Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird 68.9.0-1.el8_0
    fixed: vendor fix RHSA-2020:2616
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird 68.9.0-1.el8_1
    fixed: vendor fix RHSA-2020:2611
  • Red Hat Enterprise Linux Client (v. 7) thunderbird 68.9.0-1.el7_8
    fixed: vendor fix RHSA-2020:2615
  • Red Hat Enterprise Linux Desktop (v. 6) thunderbird 68.9.0-1.el6_10 Red Hat Enterprise Linux Server Optional (v. 6) thunderbird 68.9.0-1.el6_10
    fixed: vendor fix RHSA-2020:2613
  • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 68.9.0-1.el7_8
    fixed: vendor fix RHSA-2020:2615
  • Red Hat Enterprise Linux Workstation (v. 6) thunderbird 68.9.0-1.el6_10
    fixed: vendor fix RHSA-2020:2613
show 1 more
  • Red Hat Enterprise Linux Workstation (v. 7) thunderbird 68.9.0-1.el7_8
    fixed: vendor fix RHSA-2020:2615

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.98% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Affected products

  • Mozilla Thunderbird

Classification

Weakness
  • CWE-319 Cleartext Transmission of Sensitive Information

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.