Vulnerability · Published May 11, 2026 · Assigned by GitHub_M
CVE-2026-41431Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted
High 8.0
In plain English
A high-severity security flaw in desktop from zen-browser. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| zen-browser | desktop | < 1.19.9b |
Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H