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

Advisory record · `GHSA-4q3h-vp4r-prv2`

- **Identifiers:** `GHSA-4q3h-vp4r-prv2` · `BIT-parse-2026-27804` · `CVE-2026-27804`
- **State:** Confirmed
- **Severity:** CVSS 9.3 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-327](https://cwe.mitre.org/data/definitions/327.html) · [CWE-345](https://cwe.mitre.org/data/definitions/345.html)
- **Tags:** [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [CWE-345](https://agentprime.io/advisories/tag/cwe-345.md)
- **Published:** 25 Feb 2026
- **Updated:** 2 Mar 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 25 Feb 2026, 23:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.3: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `parse-server` (npm): affected `>=9.0.0, <9.3.1-alpha.4 || <8.6.3`; fixed in `9.3.1-alpha.4`, `8.6.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.3 Critical, CVSS 4.0: `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`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0020, the 10th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 25 Feb 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-4q3h-vp4r-prv2](https://github.com/advisories/GHSA-4q3h-vp4r-prv2)
- [OSV: GHSA-4q3h-vp4r-prv2](https://osv.dev/vulnerability/GHSA-4q3h-vp4r-prv2)
- <https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-27804>
- <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>
- <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>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-4q3h-vp4r-prv2>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-4q3h-vp4r-prv2/>. Everything for agents: <https://agentprime.io/llms.txt>.