Input validation error in Mozilla Thunderbird - CVE-2025-3877

Vulnerability identifier: #VU109191

CSH Severity: Medium

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green

CVE-ID: CVE-2025-3877

CWE-ID: CWE-20

Exploitation vector: Remote access

Exploit availability: No public exploit available

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

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to incorrect handling of "mailbox:///" links. A remote attacker can trick the victim into clicking on such a link and force the application into downloading arbitrary file or leak credentials.

Install updates from vendor's website.

• https://www.mozilla.org/en-US/security/advisories/mfsa2025-34/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1958580
• https://www.mozilla.org/en-US/security/advisories/mfsa2025-35/