CVE-2026-106503 in Backstage
Summary
by MITRE • 10/07/2026
Backstage is an open framework for building developer portals. Prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0, the @backstage/plugin-scaffolder-backend package is affected by scaffolder action input authorization bypass. An authenticated user with access to affected Scaffolder templates could bypass configured action restrictions. Depending on integration credentials, this could grant unauthorized access to repositories and related source-control resources. This issue is fixed in versions 3.3.1, 3.4.1, 4.0.3 and 4.1.0.
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Analysis
by VulDB Data Team • 10/07/2026
The Backstage developer portal framework provides a centralized platform for managing software infrastructure, including service catalogs, documentation, and CI/CD pipelines. A critical security flaw was identified within the @backstage/plugin-scaffolder-backend package prior to versions 3.3.1, 3.4.1, 4.0.3, and 4.1.0. This vulnerability stems from an authorization bypass mechanism in the scaffolding actions logic. The Scaffolder plugin allows developers to define templates that automate software creation tasks, such as generating new microservices or updating infrastructure configurations. These templates often require specific permissions to interact with external systems like Git repositories, cloud providers, and package registries.
The core technical flaw involves insufficient validation of user privileges when executing scaffolding actions. In the affected versions, an authenticated user who has access to a Scaffolder template could manipulate input parameters or exploit logic gaps to bypass configured action restrictions. This means that even if strict policies were defined to limit which users can trigger certain types of builds or deployments, the backend did not adequately enforce these constraints during runtime execution. The vulnerability essentially allows a lower-privileged user to perform actions reserved for higher-privileged roles by circumventing the intended access control checks embedded in the scaffolder configuration.
The operational impact of this authorization bypass is significant due to the nature of developer portals acting as gateways to critical development infrastructure. If an attacker or malicious insider exploits this flaw, they could gain unauthorized access to source code repositories and related version control resources. Depending on how Backstage is integrated with external systems via service accounts or API keys stored within template configurations, the compromised user might be able to push malicious code, exfiltrate sensitive intellectual property, or disrupt continuous integration pipelines. This represents a severe risk to software supply chain integrity, as it undermines the principle of least privilege and allows lateral movement into deeper parts of the development ecosystem that are typically isolated from general developer access.
This vulnerability aligns with CWE-269, which describes Improper Privilege Management, specifically where an actor is able to elevate privileges or bypass restrictions due to flawed logic in authorization checks. From a threat modeling perspective using MITRE ATT&CK techniques, this behavior corresponds to T1078 Valid Accounts and potentially T1534 Internal Spearphishing if used for social engineering within the organization, but more directly it reflects unauthorized access patterns seen in privilege escalation scenarios where system controls are bypassed rather than broken through brute force. The lack of strict enforcement on action inputs allows attackers to leverage legitimate credentials against protected resources without triggering typical anomaly detection systems that rely on explicit permission denials.
To mitigate this risk, organizations running Backstage must immediately upgrade the @backstage/plugin-scaffolder-backend package to version 3.3.1, 3.4.1, 4.0.3, or 4.1.0 and later releases where these authorization checks have been hardened. In addition to patching, administrators should review existing Scaffolder templates to ensure that no sensitive credentials are hardcoded directly into template definitions without proper secret management integration using tools like HashiCorp Vault or AWS Secrets Manager. It is also advisable to implement rigorous code reviews for any custom scaffolding actions and enable detailed audit logging on the Backstage backend to monitor for unusual patterns of template execution by users who do not typically require elevated privileges. Regular security assessments focusing on identity and access management within developer portals are essential to maintain a secure software development lifecycle environment.