CVE-2026-27804

Description

### Impact 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. ### Patches The fix 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. ### Workarounds Disable Google authentication until you can upgrade. ### References - GitHub advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2 - Fixed in Parse Server 9.3.1-alpha.4: https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4 - Fixed in Parse Server 8.6.3: https://github.com/parse-community/parse-server/releases/tag/8.6.3

How to fix CVE-2026-27804

To remediate CVE-2026-27804, upgrade the affected package to a fixed version below.

• —upgrade to 8.6.3 or later
• —upgrade to 9.3.1-alpha.4 or later

Is CVE-2026-27804 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 8.6.3, >= 9.0.0, < 9.3.1
• >= 9.0.0, < 9.3.1-alpha.4

CVSS scores

References (7)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-27804
• PATCHgithub.com/parse-community/parse-server
• WEBgithub.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7
• WEBgithub.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330