Vulnerability · Published Feb 25, 2026 · Assigned by GitHub_M

CVE-2026-27804Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter

Critical 9.3

In plain English

A critical-severity broken cryptography in parse-server from parse-community. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)9.3Critical

Exploit odds (30 days)0.2%top 90.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	parse-server	9.3.1-alpha.4	GHSA-4q3h-vp4r-prv2
npm	parse-server	8.6.3	GHSA-4q3h-vp4r-prv2

Affected products (as reported)

Vendor	Product	Versions
parse-community	parse-server	>= 9.0.0, < 9.3.1-alpha.4< 8.6.3

Weakness: CWE-327, CWE-345 · Vector: 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

References

https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2 x_refsource_CONFIRM
https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7 x_refsource_MISC
https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330 x_refsource_MISC
https://github.com/parse-community/parse-server/releases/tag/8.6.3 x_refsource_MISC
https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4 x_refsource_MISC