CVE-2026-70665 Doorkeeper OpenID Connect: DCR endpoint persists unvalidated client-supplied scopes
Attackers can register clients with unauthorized scopes to gain elevated access in Rails applications using Doorkeeper OpenID Connect.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-70665?
CVE-2026-70665 is a medium-severity vulnerability in doorkeeper-gem doorkeeper-openid_connect, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Doorkeeper OpenID Connect implements an OpenID Connect authentication provider for Rails applications on top of Doorkeeper. Prior to 1.10.4, the Dynamic Client Registration (DCR) endpoint persists client-supplied scopes without validating them against the server's configured scope set. Under certain conditions, this allows a self-registered client to obtain scopes beyond what the server intended to grant. In DynamicClientRegistrationController#application_params, the scopes attribute is assigned directly from params[:scope] with no validation against Doorkeeper.configuration.scopes or optional_scopes. Combined with enforce_configured_scopes being off by default and Doorkeeper's ScopeChecker prioritizing application-level scopes over server-level scopes, this creates a privilege escalation path. This issue is fixed in version 1.10.4.
Weakness: CWE-285
Which versions are affected by CVE-2026-70665?
How do I fix CVE-2026-70665?
Upgrade to a fixed version.
Is CVE-2026-70665 being exploited?
There is no known exploitation of CVE-2026-70665 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-70665, GHSA-8r7r-wh7x-27ff, UBUNTU-CVE-2026-70665.