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Vulnerability Details :

CVE-2026-41431

Summary
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
Published At-11 May, 2026 | 16:55
Updated At-11 May, 2026 | 18:31
Rejected At-
Credits

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

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.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:GitHub_M
Assigner Org ID:a0819718-46f1-4df5-94e2-005712e83aaa
Published At:11 May, 2026 | 16:55
Updated At:11 May, 2026 | 18:31
Rejected At:
▼CVE Numbering Authority (CNA)
Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted

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
Vendor
zen-browser
Product
desktop
Versions
Affected
  • < 1.19.9b
Problem Types
TypeCWE IDDescription
CWECWE-347CWE-347: Improper Verification of Cryptographic Signature
Type: CWE
CWE ID: CWE-347
Description: CWE-347: Improper Verification of Cryptographic Signature
Metrics
VersionBase scoreBase severityVector
3.18.0HIGH
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Version: 3.1
Base score: 8.0
Base severity: HIGH
Vector:
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
x_refsource_CONFIRM
https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e
x_refsource_MISC
Hyperlink: https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
Resource:
x_refsource_CONFIRM
Hyperlink: https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e
Resource:
x_refsource_MISC
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
exploit
Hyperlink: https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
Resource:
exploit
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:security-advisories@github.com
Published At:11 May, 2026 | 18:16
Updated At:11 May, 2026 | 19:16

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.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary3.18.0HIGH
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Type: Secondary
Version: 3.1
Base score: 8.0
Base severity: HIGH
Vector:
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
CPE Matches
Weaknesses
CWE IDTypeSource
CWE-347Secondarysecurity-advisories@github.com
CWE ID: CWE-347
Type: Secondary
Source: security-advisories@github.com
Evaluator Description
Evaluator Impact

Evaluator Solution

Vendor Statements
References
HyperlinkSourceResource
https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54esecurity-advisories@github.com
N/A
https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6qsecurity-advisories@github.com
N/A
https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q134c704f-9b21-4f2e-91b3-4a467353bcc0
N/A
Hyperlink: https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e
Source: security-advisories@github.com
Resource: N/A
Hyperlink: https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
Source: security-advisories@github.com
Resource: N/A
Hyperlink: https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Resource: N/A

Change History

0
Information is not available yet

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