CVE-2026-59387: Broken access control restriction in Cloud Controller API
The Nginx routing configuration for Cloud Controller blocks unauthenticated access to /internal/v4/ and /internal/v5/ endpoints but omits an equivalent deny rule for /internal/v3/. As a result, the staging callback endpoints /internal/v3/staging/:guid/dropletcompleted and /internal/v3/staging/:guid/buildcompleted are reachable from the public API listener without OAuth or mutual TLS.
An attacker with a valid build or droplet GUID can submit a forged staging callback, transition a droplet to STAGED, and persist arbitrary process metadata and sidecar data with no associated package or actor. A SpaceAuditor can enumerate GUIDs without write permissions, making this an effective privilege escalation beyond the intended role boundary.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Add an equivalent deny rule for /internal/v3/ to block unauthenticated public access, matching the existing restrictions for /internal/v4/ and /internal/v5/.
Nginx routing configuration for Cloud Controller Unauthenticated access to /internal/v3/ = deny
Event History
Frequently Asked Questions
Who is realistically able to exploit this issue?
An attacker needs a valid build or droplet GUID. A user with the SpaceAuditor role can enumerate these GUIDs without write permissions, allowing escalation beyond that role's intended access boundary.
Does exploitation require OAuth credentials or mutual TLS?
No. The affected /internal/v3/ staging callback endpoints are reachable through the public API listener without OAuth or mutual TLS.
What can an attacker do after reaching an affected endpoint?
They can submit a forged droplet_completed or build_completed staging callback, transition a droplet to STAGED, and persist arbitrary process metadata and sidecar data without an associated package or actor.