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9.3
Parse Server: Hackers can take control of any user account linked to Google
CVE-2026-27804
GHSA-4q3h-vp4r-prv2
Summary
Attackers can log in as any user linked to a Google account without their password. This affects all Parse Server deployments that use Google authentication. To fix, update to version 9.3.1-alpha.4 or 8.6.3, or temporarily disable Google authentication until the update is possible.
What to do
- Update parseadmin parse-server to version 9.3.1-alpha.4.
- Update parseadmin parse-server to version 8.6.3.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| parseadmin | parse-server | > 9.0.0 , <= 9.3.1-alpha.3 | 9.3.1-alpha.4 |
| parseadmin | parse-server | <= 8.6.2 | 8.6.3 |
| parseplatform | parse-server | <= 8.6.3 | – |
| parseplatform | parse-server | > 9.0.0 , <= 9.3.1 | – |
| parseplatform | parse-server | 9.3.1 | – |
| parseplatform | parse-server | 9.3.1 | – |
| parseplatform | parse-server | 9.3.1 | – |
Original title
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
Original 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
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
nvd CVSS3.1
9.1
nvd CVSS4.0
9.3
Vulnerability type
CWE-327
Use of a Broken Cryptographic Algorithm
CWE-345
- https://nvd.nist.gov/vuln/detail/CVE-2026-27804
- https://github.com/advisories/GHSA-4q3h-vp4r-prv2
- https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c... Patch
- https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05... Patch
- https://github.com/parse-community/parse-server/releases/tag/8.6.3 Release Notes
- https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4 Release Notes
- https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp... Patch Vendor Advisory
Published: 25 Feb 2026 · Updated: 12 Mar 2026 · First seen: 6 Mar 2026