Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted

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Summary

CVECVE-2026-41431
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-11 18:16:34 UTC
Updated2026-05-11 19:16:22 UTC
DescriptionZen 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.

Risk And Classification

Primary CVSS: v3.1 8 HIGH from [email protected]

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

EPSS: 0.000360000 probability, percentile 0.106380000 (date 2026-05-12)

Problem Types: CWE-347 | CWE-347 CWE-347: Improper Verification of Cryptographic Signature

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8HIGHCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
3.1CNADECLARED8HIGHCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zen-browser Desktop affected < 1.19.9b Not specified

References

ReferenceSourceLinkTags
github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843... [email protected] github.com
github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
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