# 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.

- **Severity:** Medium 4.2 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N`)
- **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:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-70665, GHSA-8r7r-wh7x-27ff, UBUNTU-CVE-2026-70665

## 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 (Improper Authorization)

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70665 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-70665 in the wild and no public exploit code.

Affected product: doorkeeper-gem doorkeeper-openid_connect. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-70665/ (Markdown: https://insights.sbomify.com/CVE-2026-70665/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70665
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70665
- OSV: https://osv.dev/vulnerability/CVE-2026-70665

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70665/
Summaries are generated and may contain mistakes; the official description above is the record.