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VulnerabilityPublished

CVE-2026-41431: zen-browser desktop · Improper Verification of Cryptographic Signature

Affects zen-browser desktopSource CVE Database V5

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Not known to be exploited · CVSS 8.0 High : upgrade to 1.19.9b soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
8.0High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.19.9b
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade zen-browser desktop to 1.19.9b.

Affected software

ProductAffectedFixed in
zen-browserdesktopAffected
  • <1.19.9b
Fixed in
  • 1.19.9b
GitHubzen-browser/desktoppkg:github/zen-browser/desktopOther threatsAffected
  • =1.19.9
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability is fixed in Zen Browser version 1.19.9b. Users and administrators should upgrade to version 1.19.9b or later to restore cryptographic signature verification for MAR updates. Since the vendor advisory does not provide additional remediation details, patch status beyond this fixed version is not explicitly stated but upgrading to 1.19.9b is the recommended action.

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.

References

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