CVE-2026-41431 json
Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted
published 2026-05-11 5 mo ago modified 2026-10-26 13 d ago also EUVD-2026-29119
- cvss
- 8.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 9%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- total
- Assessed
- 5 mo ago
Exploit prediction
0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.0 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H |
Affected products
- zen-browser desktop
Classification
- Weakness
-
- CWE-347 Improper Verification of Cryptographic Signature
References
Sources
- CVE List CVE-2026-41431
- NVD CVE-2026-41431
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