Vulnerability-Lookup

CVE-2026-41427 (GCVE-0-2026-41427)

Vulnerability from cvelistv5 – Published: 2026-04-24 19:23 – Updated: 2026-04-27 13:42

Title

Better Auth OAuth 2.1 Provider: Unprivileged users can register OAuth clients

Summary

Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.5, the clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted — any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata. This vulnerability is fixed in 1.6.5.

Severity

7.1 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:L/SA:N

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/better-auth/better-auth/securi…	x_refsource_CONFIRM

Impacted products

2 products

Vendor	Product	Version
better-auth	better-auth	Affected: >= 1.4.8-beta.7, < 1.6.5 Affected: >= 1.7.0-beta.0, <= 1.7.0-beta.1
better-auth	oauth-provider	Affected: >= 1.4.8-beta.7, < 1.6.5 Affected: >= 1.7.0-beta.0, <= 1.7.0-beta.1

Show details on NVD website

JSON

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FKIE_CVE-2026-41427

Vulnerability from fkie_nvd - Published: 2026-04-24 20:16 - Updated: 2026-05-13 19:36

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/better-auth/better-auth/security/advisories/GHSA-xr8f-h2gw-9xh6	Mitigation, Vendor Advisory

Impacted products

Vendor	Product	Version
better-auth	better-auth\/oauth-provider	*
better-auth	better-auth\/oauth-provider	1.4.8
better-auth	better-auth\/oauth-provider	1.4.8
better-auth	better-auth\/oauth-provider	1.7.0

JSON

To clipboard

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GHSA-XR8F-H2GW-9XH6

Vulnerability from github – Published: 2026-04-16 22:44 – Updated: 2026-04-27 15:24

Summary

OAuth 2.1 Provider: Unprivileged users can register OAuth clients

Details

Am I affected?

You're affected if all of the following are true:

Using @better-auth/oauth-provider at version specified below
You configured clientPrivileges in the plugin options expecting it to gate who can create OAuth clients
The /oauth2/create-client or /admin/oauth2/create-client endpoints are reachable by authenticated users you don't fully trust

If clientPrivileges is not configured, this bug has no security consequence for your deployment

### Summary

The clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted — any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata.

Non-create operations (read, list, update, delete, rotate) enforced the hook correctly. Only the create path was missing the check.

Impact

Unauthorized registration of OAuth clients by any authenticated user, under deployments that expected clientPrivileges to block them.
Attacker-controlled redirect_uris on those clients enable phishing flows that present as registered first-party applications.
If the SERVER_ONLY admin creation endpoint is also exposed to low-privilege users (a separate deployment misconfiguration), additional sensitive fields including skip_consent become writable.

Patches

Fixed in @better-auth/oauth-provider@1.6.5 Both create endpoints now call the clientPrivileges hook with action "create" before persisting the client record.

Workarounds

If you cannot upgrade immediately:

Block the /oauth2/create-client and /admin/oauth2/create-client routes at your reverse proxy or middleware layer for any user who should not be able to register clients.
Do not expose the admin creation endpoint (it is SERVER_ONLY by design and should not be reachable by end-user sessions).

Severity

8.4 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:N/SC:L/SI:H/SA:N

Show details on source website

JSON

To clipboard

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    "github_reviewed_at": "2026-04-16T22:44:27Z",
    "nvd_published_at": "2026-04-24T20:16:27Z",
    "severity": "HIGH"
  },
  "details": "### Am I affected?\n\n  You\u0027re affected if all of the following are true:\n\n  - Using @better-auth/oauth-provider at version specified below \n  - You configured clientPrivileges in the plugin options expecting it to gate who can create OAuth clients\n  - The /oauth2/create-client or /admin/oauth2/create-client endpoints are reachable by authenticated users you don\u0027t fully trust\n\n  If clientPrivileges is not configured, this bug has no security consequence for your deployment\n\n  ---\n  ### Summary\n\n  The clientPrivileges option documents a create action, but the OAuth client creation endpoints did not invoke the hook before persisting new clients. Deployments that configured clientPrivileges to restrict client registration were not actually restricted \u2014 any authenticated user could reach the create endpoints and register an OAuth client with attacker-chosen redirect URIs and metadata.\n\n Non-create operations (read, list, update, delete, rotate) enforced the hook correctly. Only the create path was missing the check.\n\n### Impact\n\n  - Unauthorized registration of OAuth clients by any authenticated user, under deployments that expected clientPrivileges to block them.\n  - Attacker-controlled redirect_uris on those clients enable phishing flows that present as registered first-party applications.\n  - If the SERVER_ONLY admin creation endpoint is also exposed to low-privilege users (a separate deployment misconfiguration), additional sensitive fields including `skip_consent` become writable.\n\n### Patches\n\nFixed in `@better-auth/oauth-provider@1.6.5` Both create endpoints now call the clientPrivileges hook with action \"create\" before persisting the client record.\n\n### Workarounds\n\n  If you cannot upgrade immediately:\n\n  - Block the /oauth2/create-client and /admin/oauth2/create-client routes at your reverse proxy or middleware layer for any user who should not be able to register clients.\n  - Do not expose the admin creation endpoint (it is SERVER_ONLY by design and should not be reachable by end-user sessions).",
  "id": "GHSA-xr8f-h2gw-9xh6",
  "modified": "2026-04-27T15:24:29Z",
  "published": "2026-04-16T22:44:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/better-auth/better-auth/security/advisories/GHSA-xr8f-h2gw-9xh6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41427"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/better-auth/better-auth"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:N/SC:L/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "OAuth 2.1 Provider: Unprivileged users can register OAuth clients"
}

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.

Action not permitted

CVE-2026-41427 (GCVE-0-2026-41427)

FKIE_CVE-2026-41427

GHSA-XR8F-H2GW-9XH6

Am I affected?

Impact

Patches

Workarounds

Tags

Sightings

Nomenclature