CVE-2026-41431 HIGH

CVE-2026-41431: Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted

Vendor Zen-Browser
Product desktop
Weakness CWE-347
Published May 11, 2026
Last update May 11, 2026
View on NVD All CVEs

CVSS base score

8.0/10
Attack vector Network
Attack complexity High
Privileges required High
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

What the vulnerability does

01Description

Zen is a firefox-based browser. Prior to 1.19.9b, Zen Browser ships a Mozilla Application Resource (MAR) updater (org.mozilla.updater) that has had all MAR signature verification stripped from the Firefox codebase it was forked from. The MAR files served to users contain zero cryptographic signatures, and the updater binary contains zero cryptographic verification code. This eliminates the defense-in-depth that MAR signing provides. If the update server or GitHub release pipeline is compromised, arbitrary unsigned code can be delivered to all Zen users via the auto-update mechanism. This vulnerability is fixed in 1.19.9b.

Key dates

02Disclosure timeline

May 11, 2026 CVE published
May 11, 2026 Record updated