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.
Published: 2026-05-11
Score: 8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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History

Tue, 12 May 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Zen-browser
Zen-browser desktop
Vendors & Products Zen-browser
Zen-browser desktop

Mon, 11 May 2026 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Mon, 11 May 2026 17:30:00 +0000

Type Values Removed Values Added
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.
Title Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted
Weaknesses CWE-347
References
Metrics cvssV3_1

{'score': 8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H'}


Subscriptions

Zen-browser Desktop
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-11T18:31:38.146Z

Reserved: 2026-04-20T15:32:33.814Z

Link: CVE-2026-41431

cve-icon Vulnrichment

Updated: 2026-05-11T18:31:33.175Z

cve-icon NVD

Status : Deferred

Published: 2026-05-11T18:16:34.280

Modified: 2026-05-13T15:37:58.427

Link: CVE-2026-41431

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-12T09:22:51Z

Weaknesses