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CVE-2026-27804

CRITICAL

Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter

Published February 25, 2026Updated March 2, 2026Source: osv

Summary

### 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

Remediation

Upgrade to the fixed version using your package manager.

npm
Update parse-server to 8.6.3 or later
npm install parse-server@8.6.3
npm
Update parse-server to 9.3.1-alpha.4 or later
npm install parse-server@9.3.1-alpha.4

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (2)

PackageEcosystemAffectedFixed In
parse-server
npm
All versions8.6.3
parse-server
npm
All versions9.3.1-alpha.4

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

  • CWE-327
    Use of a Broken or Risky Cryptographic AlgorithmMITRE
  • CWE-345
    Insufficient Verification of Data AuthenticityMITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.1 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
—
Confidentiality
—
Integrity
—
Availability
—

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

Frequently Asked Questions

What is CVE-2026-27804?
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.1/10).
How do I check if my project is affected by CVE-2026-27804?
CVE-2026-27804 affects parse-server. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-27804 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.1

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-4q3h-vp4r-prv2
BIT-parse-2026-27804

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