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Vulnerability record · CVE-2026-41431 · published 11 May 2026

CVE-2026-41431: Improper verification of cryptographic signature vulnerability

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.

8.0 CVSS 3.1 High EPSS 0.27% · top 82.4% CWE-347 · Improper verification of cryptographic signature Deferred
8.0CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-41431), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.