OpenBao is an open source identity-based secrets management system. Prior to 2.5.5, an OpenBao user with access to sys/leases/revoke/:lease_id in one namespace could revoke a lease in another namespace when the foreign lease_id was known, bypassing namespace ACL isolation. The affected lease lookup routing in vault/expiration.go allowed FetchLeaseInfo and loadEntry to resolve cached or stored lease data outside the request namespace, allowing a tenant that intentionally disclosed a lease identifier to have the lease and its underlying credential revoked by another tenant. This issue is fixed in version 2.5.5.