---
title: "CVE-2026-27804: Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter"
url: https://erroneo.us/security/cve/CVE-2026-27804/
description: "CVE-2026-27804 (parse-server (npm)): Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-25
date_modified: 2026-02-27
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-27804"
kev: false
cvss: 9.3
epss: 0.00237
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.2% , percentile 14: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 14% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes parse-server (npm) >= 9.0.0, <= 9.3.1-alpha.3, fixed in 9.3.1-alpha.4 ; parse-server (npm) <= 8.6.2, fixed in 8.6.3 . Check your lockfile, including transitive dependencies.

## What it is

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 packages

- npm `parse-server` >= 9.0.0, <= 9.3.1-alpha.3 → fixed: 9.3.1-alpha.4
- npm `parse-server` <= 8.6.2 → fixed: 8.6.3

## Affected products (CVE record)

- parse-community parse-server: >= 9.0.0, < 9.3.1-alpha.4, < 8.6.3

## Severity

- GitHub_M CVSS 4.0: 9.3 `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`
- GitHub CVSS 4.0: 9.3 `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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.24% probability of exploitation activity in the next 30 days; percentile 14.

## Sources

- [GitHub Advisory GHSA-4q3h-vp4r-prv2](https://github.com/advisories/GHSA-4q3h-vp4r-prv2)
- [CVE.org record CVE-2026-27804](https://www.cve.org/CVERecord?id=CVE-2026-27804)
- [NVD entry CVE-2026-27804](https://nvd.nist.gov/vuln/detail/CVE-2026-27804)
- [github.com](https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2)
- [github.com](https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7)
- [github.com](https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330)
- [github.com](https://github.com/parse-community/parse-server/releases/tag/8.6.3)
- [github.com](https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4)

---
Source page: https://erroneo.us/security/cve/CVE-2026-27804/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt