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CVE-2026-41431

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

Published: May 11, 2026Updated: May 13, 2026 Sources: CVE List NVDCWE-347
NVD MITRE
8.0CVSSHIGH
EPSS Score
0.2%
Top 90.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

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.

CVSS Vector Breakdown

AV:NAC:HPR:HUI:NS:CC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:HPrivileges Required
High
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-347

Affected Products

desktopzen-browser
Mixed
Consumer Software / browser
zen-browseross-projectConsumer Softwareaka desktop

Attack Graph

Products CVE Techniques Tactics

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Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

1 technique
Collection
View detailed technique mapping

References

https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
github.com
https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e
github.com

Timeline

Published
May 11, 2026
Last Updated
May 13, 2026

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