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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-41431
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 08:33 UTC · Revision 1
Source evidence
Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted
core-osv · Original sourcePublished 11 May 2026, 16:55 UTC
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.
osv:CVE-2026-41431
Complete source record
{
"id": "5f2be9db124d915ea2b828758eba8ed1d9d57b15a9fa1c0bc8b514b4bf2c629e",
"url": "https://osv.dev/vulnerability/CVE-2026-41431",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Zen Browser MAR updater ships with signature verification removed — unsigned updates accepted",
"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.",
"evidence": "osv:CVE-2026-41431",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-41431",
"aliases": [
"CVE-2026-41431",
"GHSA-qpj9-m8jc-mw6q"
],
"metrics": [
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"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/zen-browser/desktop",
"type": "GIT",
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{
"fixed": "98e18d5f604b9d140fe32b5dd997322562a29bb7"
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{
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"strategy": "StringRangeExpression"
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"source": "REFERENCES_COMMIT"
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-41431.json"
}
}
],
"modified": "2026-10-28T02:30:27.090748331Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41431.json",
"https://github.com/zen-browser/desktop/security/advisories/GHSA-qpj9-m8jc-mw6q",
"https://nvd.nist.gov/vuln/detail/CVE-2026-41431",
"https://github.com/zen-browser/desktop/commit/270db6d6713d2c6c14d9df0b4bc7662843d3d54e"
],
"provider_metadata": {
"cwe_ids": [
"CWE-347"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41431.json"
}
},
"related_cves": [
{
"value": "CVE-2026-41431",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 493854,
"published_at": "2026-05-11T16:55:10.814+00:00"
}