OpenStack Keystone provides authentication, authorization, and service discovery for OpenStack. Grzegorz Grasza (Red Hat) and Tim Shephard (roiai.ca) independently identified that Keystone does not consistently enforce scope restrictions on tokens obtained via delegated authentication methods (ec2credential, application credential, OAuth1 access tokens).

This flaw covers Launchpad #2153453 (delegation bypass in trust, OAuth1, and application credential operations). In keystone/api/trusts.py, _check_application_credential() only checked for 'application_credential' in token.methods, allowing EC2 credential tokens (methods: ['ec2credential']) and OAuth1 tokens (methods: ['oauth1']) to perform trust CRUD operations. Similarly, _block_delegated_token_app_creds() in keystone/api/users.py only checked trust_id and access_token_id attributes, allowing EC2 tokens to manage application credentials. AuthorizeResource.put in keystone/api/os_oauth1.py checked ctx.is_delegated_auth and 'application_credential' in methods, but EC2 tokens set neither flag. Trust role validation in _get_trustor_roles() checks the trustor's full role assignments rather than the token's scoped roles, enabling role escalation.

An attacker with a limited-scope EC2 or OAuth1 credential can create trusts that delegate the user's full role set, create persistent application credentials, and authorize new OAuth1 delegations. Those derived credentials survive revocation of the original delegated credential.

Upstream affected range: Keystone >=13.0.0 through unfixed 27.x, 28.x, and 29.x releases. Proposed patches use a _PRIMARY_AUTH_METHODS allowlist and reject tokens whose methods are not entirely in that set. On current master, a separate middleware guard in auth_context.py globally rejects EC2 credential tokens from API authorization, but that guard is not present on stable branches.

CVE IDs have been requested by the OpenStack Vulnerability Management Team and are not yet assigned (CVE-2026-pending).
Reporter: Grzegorz Grasza (Red Hat) and Tim Shephard (roiai.ca). Coordinated by Goutham Pacha Ravi, OpenStack VMT.
Private Launchpad report: https://launchpad.net/bugs/2153453
PSIRT Ticket: PSIRTSUPT-21454