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Fencer Vulns
medium 6.5

CVE-2018-12373 json

dDecrypted S/MIME parts hidden with CSS or the plaintext HTML tag can leak plaintext when included in a HTML reply/forward.

published 2018-10-18 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-4347

cvss
6.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.4%
EPSS 2.4% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

dDecrypted S/MIME parts hidden with CSS or the plaintext HTML tag can leak plaintext when included in a HTML reply/forward. This vulnerability affects Thunderbird < 52.9.

Patch / fix

  • Mozilla Thunderbird 52.9
  • thunderbird Debian 14, Debian 13, Debian 12 1:52.9.0-1

debian advisories DEBIAN-CVE-2018-12373

  • thunderbird Ubuntu 14.04 LTS 1:52.9.1+build3-0ubuntu0.14.04.1
  • thunderbird Ubuntu 16.04 LTS 1:52.9.1+build3-0ubuntu0.16.04.1
  • thunderbird Ubuntu 18.04 LTS 1:52.9.1+build3-0ubuntu0.18.04.1

ubuntu advisories UBUNTU-CVE-2018-12373

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 52.9.1-1.el7_5
  • thunderbird RHEL 6 52.9.1-1.el6

red hat advisories RHSA-2018:2252RHSA-2018:2251

  • MozillaThunderbird SLE Workstation Extension 15 52.9.1-3.7.1

suse advisories SUSE-SU-2018:2174-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1

opensuse advisories openSUSE-SU-2024:10601-1

  • thunderbird Arch Linux 52.9.1-1

arch linux advisories AVG-728

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-2018-12373 updated cvss 6.5

thunderbird: S/MIME plaintext can be leaked through HTML reply/forward

  • Red Hat Enterprise Linux Client (v. 7) thunderbird 52.9.1-1.el7_5
    fixed: vendor fix RHSA-2018:2252
  • Red Hat Enterprise Linux Desktop (v. 6) thunderbird 52.9.1-1.el6
    fixed: vendor fix RHSA-2018:2251
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server Optional (v. 7) thunderbird 52.9.1-1.el7_5
    fixed: vendor fix RHSA-2018:2252
  • Red Hat Enterprise Linux Server Optional (v. 6) thunderbird 52.9.1-1.el6
    fixed: vendor fix RHSA-2018:2251
  • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 52.9.1-1.el7_5
    fixed: vendor fix RHSA-2018:2252
  • Red Hat Enterprise Linux Workstation (v. 6) thunderbird 52.9.1-1.el6
    fixed: vendor fix RHSA-2018:2251
  • Red Hat Enterprise Linux Workstation (v. 7) thunderbird 52.9.1-1.el7_5
    fixed: vendor fix RHSA-2018:2252
  • Red Hat Enterprise Linux 8 thunderbird
    not affected: vulnerable code not present

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

2.40% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 6.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/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-200 Exposure of Sensitive Information to an Unauthorized Actor

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.