CVE-2026-106563 in Backstage
Summary
by MITRE • 10/07/2026
Backstage is an open framework for building developer portals. Prior to 0.21.8, the @backstage/plugin-kubernetes-backend package is affected by improper entity validation in deprecated kubernetes services endpoint. An authenticated user with Kubernetes read permissions could access Kubernetes workload data beyond their intended scope by supplying crafted entity data to the deprecated services endpoint. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters. This issue is fixed in version 0.21.8.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified within the Backstage developer portal framework, specifically affecting versions prior to 0.21.8, centers on an improper entity validation flaw located in the deprecated Kubernetes services endpoint of the @backstage/plugin-kubernetes-backend package. This security issue arises from insufficient input sanitization and authorization checks when processing requests directed at this legacy interface. The core technical deficiency lies in the backend's failure to strictly validate that the entity data supplied by a user corresponds exclusively to resources they are explicitly authorized to access within their designated Kubernetes namespace or cluster scope. Consequently, an attacker who has successfully authenticated to the Backstage platform and possesses basic read permissions for Kubernetes objects can manipulate request parameters to target entities outside of their intended operational boundaries. This represents a classic instance of broken object level authorization where the application logic does not adequately enforce separation between distinct tenant or user contexts when querying backend services.
From an offensive security perspective, this vulnerability aligns with CWE-284 Improper Access Control and specifically reflects patterns associated with CWE-639 Authorization Bypass Through User-Controlled Key in web applications. The exploitation vector requires the attacker to be a legitimate authenticated user, which classifies this as an insider threat or compromised credential scenario rather than an unauthenticated remote code execution risk. By supplying crafted entity identifiers within API requests sent to the deprecated endpoint, the malicious actor can bypass standard namespace isolation mechanisms enforced by Kubernetes RBAC policies at the application layer. The backend processes these requests and returns metadata for workloads such as pods, deployments, or services that belong to other users or sensitive production environments, effectively allowing lateral movement across logical boundaries within the multi-tenant developer portal environment.
The operational impact of this vulnerability is primarily confined to information disclosure rather than system compromise or data modification. The exposure is limited to read-only access for Kubernetes object metadata, meaning an attacker cannot execute commands on cluster nodes, modify configurations, or disrupt service availability directly through this flaw. However, the leakage of sensitive infrastructure details poses significant risks in enterprise environments where Backstage serves as a central hub for developer tooling. Exposed metadata can reveal internal architecture patterns, version numbers of running services, and potentially expose endpoints that could be further targeted by more sophisticated attacks. In regulated industries or organizations with strict data classification policies, the unauthorized aggregation of infrastructure intelligence violates compliance requirements regarding least privilege access and data segregation.
To mitigate this risk, organizations must immediately upgrade to Backstage version 0.21.8 or later where the validation logic in the Kubernetes backend has been corrected to enforce stricter entity scoping rules. For environments that cannot update immediately due to dependency constraints, it is critical to disable or restrict access to the deprecated services endpoint if possible through network-level controls such as firewall rules or API gateway policies. Additionally, administrators should review existing RBAC configurations within their Kubernetes clusters and Backstage catalog entities to ensure that user permissions are granularly defined according to the principle of least privilege. Regular audits of authentication logs can help detect anomalous access patterns indicative of exploitation attempts against this specific endpoint before significant data exposure occurs.