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Fencer Vulns
medium 4.3

CVE-2020-12397 json

By encoding Unicode whitespace characters within the From email header, an attacker can spoof the sender email address that Thunderbird dis…

published 2020-05-22 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4709

cvss
4.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

By encoding Unicode whitespace characters within the From email header, an attacker can spoof the sender email address that Thunderbird displays. This vulnerability affects Thunderbird < 68.8.0.

Patch / fix

  • Mozilla Thunderbird 68.8.0
  • thunderbird Debian 14, Debian 13, Debian 12 1:68.8.0-1

debian advisories DEBIAN-CVE-2020-12397

  • thunderbird Ubuntu 16.04 LTS 1:68.8.0+build2-0ubuntu0.16.04.2
  • thunderbird Ubuntu 18.04 LTS 1:68.8.0+build2-0ubuntu0.18.04.2
  • thunderbird Ubuntu 20.04 LTS 1:68.8.0+build2-0ubuntu0.20.04.2

ubuntu advisories UBUNTU-CVE-2020-12397

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 68.8.0-1.el7_8
  • thunderbird RHEL 8 68.8.0-1.el8_2
  • thunderbird RHEL 6 68.8.0-1.el6_10
  • thunderbird RHEL 8.1 EUS 68.8.0-1.el8_1
  • thunderbird RHEL 8.0 E4S 68.8.0-1.el8_0

red hat advisories RHSA-2020:2050RHSA-2020:2046RHSA-2020:2049RHSA-2020:2047RHSA-2020:2048

  • MozillaThunderbird SLE Workstation Extension 15 SP1 68.8.0-3.80.2

suse advisories SUSE-SU-2020:1225-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.1 68.8.0-lp151.2.38.2

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2020:0643-1

  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 68.8.0-r0

alpine advisories ALPINE-CVE-2020-12397

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 68.8.0-1

arch linux advisories AVG-1155

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-2020-12397 updated cvss 4.3

Mozilla: Sender Email Address Spoofing using encoded Unicode characters

  • Red Hat Enterprise Linux 5 thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) thunderbird 68.8.0-1.el8_2
    fixed: vendor fix RHSA-2020:2046
  • Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird 68.8.0-1.el8_0
    fixed: vendor fix RHSA-2020:2048
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird 68.8.0-1.el8_1
    fixed: vendor fix RHSA-2020:2047
  • Red Hat Enterprise Linux Client (v. 7) thunderbird 68.8.0-1.el7_8
    fixed: vendor fix RHSA-2020:2050
  • Red Hat Enterprise Linux Desktop (v. 6) thunderbird 68.8.0-1.el6_10 Red Hat Enterprise Linux Server Optional (v. 6) thunderbird 68.8.0-1.el6_10
    fixed: vendor fix RHSA-2020:2049
  • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 68.8.0-1.el7_8
    fixed: vendor fix RHSA-2020:2050
  • Red Hat Enterprise Linux Workstation (v. 6) thunderbird 68.8.0-1.el6_10
    fixed: vendor fix RHSA-2020:2049
show 1 more
  • Red Hat Enterprise Linux Workstation (v. 7) thunderbird 68.8.0-1.el7_8
    fixed: vendor fix RHSA-2020:2050

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

0.61% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

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

Affected products

  • Mozilla Thunderbird

Classification

Weakness

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.