Critical
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
Type: advisorySources: OSV
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with `alg: "none"` to log in as any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with `jwks-rsa` which rejects unknown key IDs. As a workaround, dsable Google authentication until upgrading is possible.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-27804
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 16:44 UTC · Revision 1
Source evidence
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
core-osv · Original sourcePublished 25 Feb 2026, 23:48 UTC
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with `alg: "none"` to log in as any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with `jwks-rsa` which rejects unknown key IDs. As a workaround, dsable Google authentication until upgrading is possible.
osv:CVE-2026-27804
Complete source record
{
"id": "d8f346ed329600680f945533fd6b8c8dd0f6de7fa50861bf00d0b5394c770c88",
"url": "https://osv.dev/vulnerability/CVE-2026-27804",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter",
"summary": "Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with `alg: \"none\"` to log in as any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with `jwks-rsa` which rejects unknown key IDs. As a workaround, dsable Google authentication until upgrading is possible.",
"evidence": "osv:CVE-2026-27804",
"products": [],
"severity": "critical",
"structured": {
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"CVE-2026-27804",
"GHSA-4q3h-vp4r-prv2"
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"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
}
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],
"modified": "2026-10-28T02:30:30.729331361Z",
"provider": "osv",
"references": [
"https://github.com/parse-community/parse-server/releases/tag/8.6.3",
"https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27804.json",
"https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2",
"https://nvd.nist.gov/vuln/detail/CVE-2026-27804",
"https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7",
"https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330"
],
"provider_metadata": {
"cwe_ids": [
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"CWE-345"
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"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27804.json"
}
},
"related_cves": [
{
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"evidence": "/id"
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"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 497526,
"published_at": "2026-02-25T23:48:20.858+00:00"
}