An issue was discovered in OpenStack Keystone before 29.0.2. POST /v3/credentials did not validate that the caller-supplied project_id for an EC2-type credential matched the project of the authenticating application credential. This allowed an attacker holding an unrestricted application credential for project A to create an EC2 credential targeting project B.

a subsequent /v3/ec2tokens exchange would then issue a Keystone token scoped to project B while still carrying the original app_cred_id, enabling cross-project lateral movement within the credential owner's role footprint.