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Fencer Vulns
medium 5.3

CVE-2018-18509 json

A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even…

published 2019-04-26 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-10234

cvss
5.3
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits
0
none known

Summary

A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even if the shown message contents aren't covered by the signature. The flaw allows an attacker to reuse a valid S/MIME signature to craft an email message with arbitrary content. This vulnerability affects Thunderbird < 60.5.1.

Patch / fix

  • Mozilla Thunderbird 60.5.1
  • thunderbird Debian 14, Debian 13, Debian 12 1:60.5.1-1

debian advisories DEBIAN-CVE-2018-18509

  • thunderbird Ubuntu 14.04 LTS 1:60.5.1+build2-0ubuntu0.14.04.1
  • thunderbird Ubuntu 16.04 LTS 1:60.5.1+build2-0ubuntu0.16.04.1
  • thunderbird Ubuntu 18.04 LTS 1:60.5.1+build2-0ubuntu0.18.04.1

ubuntu advisories UBUNTU-CVE-2018-18509

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 8 60.6.1-1.el8
  • thunderbird RHEL 7 60.6.1-1.el7_6
  • thunderbird RHEL 6 60.6.1-1.el6_10

red hat advisories RHSA-2019:1144RHSA-2019:0681RHSA-2019:0680

  • MozillaThunderbird SLE Workstation Extension 15 60.6.1-3.28.1
  • MozillaThunderbird SLE Workstation Extension 15 60.5.1-3.24.1

suse advisories SUSE-SU-2019:0853-1SUSE-SU-2019:0469-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.0 60.6.1-lp150.3.37.1
  • MozillaThunderbird Package Hub 12 60.5.1-79.1

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2019:1162-1openSUSE-SU-2019:0249-1

  • thunderbird Arch Linux 60.5.1-1

arch linux advisories AVG-908

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-2018-18509 updated cvss 5.3

thunderbird: flaw in verification of S/MIME signature resulting in signature spoofing

  • Red Hat Enterprise Linux AppStream (v. 8) thunderbird 60.6.1-1.el8
    fixed: vendor fix RHSA-2019:1144
  • Red Hat Enterprise Linux Client (v. 7) thunderbird 60.6.1-1.el7_6
    fixed: vendor fix RHSA-2019:0681
  • Red Hat Enterprise Linux Desktop (v. 6) thunderbird 60.6.1-1.el6_10
    fixed: vendor fix RHSA-2019:0680
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server Optional (v. 7) thunderbird 60.6.1-1.el7_6
    fixed: vendor fix RHSA-2019:0681
  • Red Hat Enterprise Linux Server Optional (v. 6) thunderbird 60.6.1-1.el6_10
    fixed: vendor fix RHSA-2019:0680
  • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird 60.6.1-1.el7_6
    fixed: vendor fix RHSA-2019:0681
  • Red Hat Enterprise Linux Workstation (v. 6) thunderbird 60.6.1-1.el6_10
    fixed: vendor fix RHSA-2019:0680
  • Red Hat Enterprise Linux Workstation (v. 7) thunderbird 60.6.1-1.el7_6
    fixed: vendor fix RHSA-2019:0681

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

1.68% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 5.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Thunderbird

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

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.