Multiple interpretations of UI input in Mozilla Thunderbird - CVE-2026-3889

Vulnerability identifier: #VU124596

CSH Severity: Low

CVSS v4: 2.1 [CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N]

CVE-ID: CVE-2026-3889

CWE-ID: CWE-450

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to perform spoofing attack.

The vulnerability exists due to improper implementation of UI. A remote attacker can send a specially crafted email to the victim and perform spoofing attack. 

Mozilla Thunderbird
Debian Linux
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Server 15
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
SUSE Package Hub 15
openSUSE Leap
openEuler
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
thunderbird (Debian package)
thunderbird (Red Hat package)
MozillaThunderbird-translations-common
MozillaThunderbird-debugsource
MozillaThunderbird-translations-other
MozillaThunderbird
MozillaThunderbird-debuginfo
thunderbird
thunderbird-debuginfo
thunderbird-debugsource
thunderbird-librnp-rnp
thunderbird-wayland

Install updates from vendor's website.

Mozilla Thunderbird - addressed in versions 140.9.0, 149.0
thunderbird (Debian package) - addressed in versions 1:140.9.0esr-1~deb12u1, 1:140.9.0esr-1~deb13u1
thunderbird (Red Hat package) - addressed in versions 140.9.0-1.el8_2, 140.9.0-1.el8_4, 140.9.0-1.el8_6, 140.9.0-1.el8_8, 140.9.0-1.el9_2, 140.9.0-1.el9_4, 140.9.0-1.el9_6, 140.9.0-1.el10_0, 140.9.0-1.el10_1
MozillaThunderbird-translations-common - update to 140.9.0-150200.8.263.1
MozillaThunderbird-debugsource - update to 140.9.0-150200.8.263.1
MozillaThunderbird-translations-other - update to 140.9.0-150200.8.263.1
MozillaThunderbird - update to 140.9.0-150200.8.263.1
MozillaThunderbird-debuginfo - update to 140.9.0-150200.8.263.1
thunderbird - update to 140.9.1-1
thunderbird-debuginfo - update to 140.9.1-1
thunderbird-debugsource - update to 140.9.1-1
thunderbird-librnp-rnp - update to 140.9.1-1
thunderbird-wayland - update to 140.9.1-1
thunderbird - update to 140.12.0-1.0.1

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-23/
• https://www.mozilla.org/en-US/security/advisories/mfsa2026-24/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2020723

• Multiple vulnerabilities in Thunderbird ESR
• Multiple vulnerabilities in Mozilla Thunderbird
• Debian update for thunderbird
• Red Hat Enterprise Linux 10 update for thunderbird
• SUSE update for MozillaThunderbird
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 10 update for thunderbird
• openEuler 24.03 LTS SP3 update for thunderbird
• openEuler 24.03 LTS SP2 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Anolis OS update for thunderbird