CVE-2026-27804
published 2026-02-26CVE-2026-27804: 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…
PriorityP266critical9.1CVSS 3.1
AVNACLPRNUINSUCHIHAN
EPSS
0.18%
7.4th percentile
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
7 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| parse-community | parse-server | < 8.6.3 | 8.6.3 |
| parse-community | parse-server | — | — |
| parse-community | parse-server | >= 0 < 8.6.3 | 8.6.3 |
| parse-community | parse-server | >= 9.0.0 < 9.3.1-alpha.4 | 9.3.1-alpha.4 |
| parseplatform | parse-server | < 8.6.3 | 8.6.3 |
| parseplatform | parse-server | — | — |
| parseplatform | parse-server | >= 9.0.0 < 9.3.1 | 9.3.1 |
CVSS provenance
nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
nvdv4.09.3CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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OSV
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
osv·2026-02-25
CVE-2026-27804 [CRITICAL] Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
### 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/
GHSA
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
ghsa·2026-02-25
CVE-2026-27804 [CRITICAL] CWE-327 Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
### 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/
No detection rules found.
No public exploits indexed.
https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330https://github.com/parse-community/parse-server/releases/tag/8.6.3https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2
2026-02-26
Published