Junglewise Threat Intelligence

Metal3 Cluster API Provider authorization bypass in cross-namespace resource access

Severity: medium · CVSS 5.5 · Published 2026-05-29

Executive brief

Metal3 Cluster API Provider (CAPM3), a tool used to manage physical computer hardware within Kubernetes, contains several security flaws that allow users to access resources outside of their assigned workspace. An authorized user with infrastructure-level permissions could potentially view sensitive configuration secrets or hijack hardware resources belonging to other teams or customers. While this primarily affects large-scale environments where multiple teams share the same management system, it could lead to unauthorized data access or service disruption.

Technical details

Four distinct authorization vulnerabilities (CWE-863) were identified in CAPM3. These include: 1) Metal3Machine accepting secret references (userData, metaData, networkData) from arbitrary namespaces; 2) Metal3Machine host annotations allowing BareMetalHost lookups in other namespaces; 3) Metal3LabelSync using incorrect logical AND operators during ConsumerRef validation; and 4) Metal3DataClaim referencing Metal3DataTemplate resources across namespace boundaries. An attacker with RBAC permissions to create or modify Metal3Machine or Metal3DataClaim resources can exploit these to read secrets or associate with unauthorized BareMetalHosts. The issues are patched in versions 1.11.8, 1.12.5, and 1.13.0.

Affected products

  • Metal3-io cluster-api-provider-metal3 <= 1.11.7, 1.12.0 - 1.12.4

Timeline

  • 2026-04-20: other: Initial fix merged in pull request 3288
  • 2026-05-18: disclosed: Advisory published by maintainers
  • 2026-05-29: advisory: GitHub Advisory Database entry updated

References