CVE-2026-106492 in Backstage
Summary
by MITRE • 10/07/2026
Backstage is an open framework for building developer portals. Prior to 0.16.1 and 0.17.8, the @backstage/backend-defaults package is affected by improper preservation of access restrictions during service credential delegation. An external service credential configured with access restrictions (e.g., read-only) could bypass those restrictions by routing requests through plugin delegation paths. This could allow a restricted service to perform operations beyond its intended scope, including write operations on plugins it was restricted to read-only access for. This issue is fixed in versions 0.16.1 and 0.17.8.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified within the Backstage developer portal framework represents a critical flaw in how service credentials manage their scope of authority during delegation processes. Backstage serves as an open-source platform for constructing internal developer portals, aggregating services from various infrastructure tooling and allowing developers to discover, provision, and monitor software. Central to its architecture is the @backstage/backend-defaults package, which handles core backend functionalities including authentication, authorization, and service credential management. The specific issue lies in the improper preservation of access restrictions when these credentials are delegated across different plugin paths or services within the application environment. This architectural weakness undermines the principle of least privilege by allowing a service with limited permissions to escalate its capabilities through indirect routing mechanisms that were not adequately secured against such bypasses.
Technically, the flaw manifests during the process where an external service credential is passed from one component to another via plugin delegation paths. When a service is configured with specific access restrictions, such as read-only access to certain resources or plugins, these constraints are intended to persist throughout its operational lifecycle within the Backstage ecosystem. However, prior to versions 0.16.1 and 0.17.8, the backend logic failed to enforce these boundaries when requests were routed through delegated plugin interfaces. Instead of maintaining the original restrictive context, the system effectively stripped or ignored the access limitations during the delegation handshake. This allows a client authenticated with restricted credentials to execute HTTP requests that target write operations on resources where they should only have read permissions. The vulnerability essentially creates an authorization bypass scenario where the identity remains valid but the associated privileges are incorrectly expanded based on the destination of the request rather than the original scope granted by the credential issuer.
The operational impact of this vulnerability is significant for organizations relying on Backstage to manage sensitive infrastructure and developer workflows. An attacker who gains access to a service account with read-only permissions could exploit this flaw to modify configurations, deploy unauthorized changes, or alter metadata within plugins they are not supposed to touch. This could lead to data integrity issues, configuration drift in production environments, or even complete compromise of the developer portal if critical settings are altered. For instance, an attacker might be able to change plugin configurations that affect how other developers interact with CI/CD pipelines or cloud resource provisioning tools integrated into Backstage. The ability to perform write operations where only read access was intended breaks the trust model between different microservices and plugins within the platform, potentially leading to broader security breaches if these services have elevated privileges on underlying infrastructure systems.
This vulnerability aligns closely with CWE-269, which describes Improper Privilege Management, specifically regarding the failure to maintain appropriate restrictions during context transitions or delegation. It also relates to CWE-862, Missing Authorization Check, as the system fails to verify that the delegated request adheres to the original credential's limitations. In terms of the MITRE ATT&CK framework, this behavior is characteristic of techniques used in lateral movement and privilege escalation within application environments, such as T1098.004 (SSH Authorized Keys) or more broadly T1528 (Steal Application Access Token), where an attacker leverages existing credentials to access resources beyond their intended scope by manipulating the authentication context. The exploitation relies on the structural design of how Backstage handles service-to-service communication, making it a sophisticated attack vector that requires understanding of the internal plugin architecture rather than simple input manipulation.
To mitigate this risk, organizations running versions of Backstage prior to 0.16.1 and 0.17.8 must upgrade immediately to one of these patched releases or any later version where the issue has been resolved. The fix ensures that access restrictions defined in service credentials are strictly preserved during all delegation paths, preventing unauthorized privilege escalation through plugin routing. In addition to upgrading, administrators should audit their current Backstage configurations for services with broad permissions and apply strict read-only constraints wherever possible to minimize the blast radius of any potential future vulnerabilities. Implementing robust logging and monitoring for API calls that involve credential delegation can also help detect anomalous behavior indicative of exploitation attempts. Regular security reviews of custom plugins and backend integrations are recommended to ensure they adhere to secure coding practices regarding authorization checks during service interactions.