An issue was discovered in OpenStack keystonemiddleware 10.5 through 10.7 before 10.7.2, 10.8 and 10.9 before 10.9.1, and 10.10 through 10.12 before 10.12.1. The external_oauth2_token middleware fails to sanitize incoming authentication headers before processing OAuth 2.0 tokens. By sending forged identity headers such as X-Is-Admin-Project, X-Roles, or X-User-Id, an authenticated attacker may escalate privileges or impersonate other users. All deployments using the external_oauth2_token middleware are affected.