GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

GHSA-4Q3H-VP4R-PRV2

Vulnerability from github – Published: 2026-02-25 23:00 – Updated: 2026-02-27 21:52
VLAI
Summary
Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter
Details

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
Severity
9.3 (Critical)
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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 9.3.1-alpha.3"
      },
      "package": {
        "ecosystem": "npm",
        "name": "parse-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "9.0.0"
            },
            {
              "fixed": "9.3.1-alpha.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 8.6.2"
      },
      "package": {
        "ecosystem": "npm",
        "name": "parse-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "8.6.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27804"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-327",
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-25T23:00:49Z",
    "nvd_published_at": "2026-02-26T00:16:25Z",
    "severity": "CRITICAL"
  },
  "details": "### Impact\n\nAn 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.\n\n### Patches\n\nThe fix hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter\u0027s custom key fetcher with `jwks-rsa` which rejects unknown key IDs.\n\n### Workarounds\n\nDisable Google authentication until you can upgrade.\n\n### References\n\n- GitHub advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2\n- Fixed in Parse Server 9.3.1-alpha.4: https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4\n- Fixed in Parse Server 8.6.3: https://github.com/parse-community/parse-server/releases/tag/8.6.3",
  "id": "GHSA-4q3h-vp4r-prv2",
  "modified": "2026-02-27T21:52:22Z",
  "published": "2026-02-25T23:00:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/parse-community/parse-server/security/advisories/GHSA-4q3h-vp4r-prv2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27804"
    },
    {
      "type": "WEB",
      "url": "https://github.com/parse-community/parse-server/commit/9b94083accb7f3e72c6b8126c195c7a03dd2dfd7"
    },
    {
      "type": "WEB",
      "url": "https://github.com/parse-community/parse-server/commit/9d5942d50e55c822924c27b05aa98f1393e7a330"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/parse-community/parse-server"
    },
    {
      "type": "WEB",
      "url": "https://github.com/parse-community/parse-server/releases/tag/8.6.3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/parse-community/parse-server/releases/tag/9.3.1-alpha.4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.