Summary
A scaffolder action input authorization bypass in Backstage may allow an authenticated user with access to affected templates to circumvent configured restrictions on actions. Depending on available integration credentials, this could enable unauthorized access to repositories and related source-control resources.
A scaffolder action input authorization bypass in Backstage may allow an authenticated user with access to affected templates to circumvent configured restrictions on actions. Depending on available integration credentials, this could enable unauthorized access to repositories and related source-control resources.
Affected context
The issue occurs in Backstage deployments using the @backstage/plugin-scaffolder-backend package when users can run affected Scaffolder templates and action restrictions are relied upon to limit permitted operations. Risk is greater where the Scaffolder backend has credentials with write or administrative access to repositories or other source-control resources.
The issue occurs in Backstage deployments using the @backstage/plugin-scaffolder-backend package when users can run affected Scaffolder templates and action restrictions are relied upon to limit permitted operations. Risk is greater where the Scaffolder backend has credentials with write or administrative access to repositories or other source-control resources.
Exploit preconditions
- Attack surface: Backstage Scaffolder template execution
- Required access: An authenticated account permitted to access affected templates
- Trigger point: Submission or execution of a template containing restricted scaffolder actions
- Why exploitation is possible: Action input authorization checks may be bypassed, allowing configured restrictions to be circumvented
- Additional dependency: The resulting impact depends on the permissions and integrations available to the Scaffolder backend
- Attack surface: Backstage Scaffolder template execution
- Required access: An authenticated account permitted to access affected templates
- Trigger point: Submission or execution of a template containing restricted scaffolder actions
- Why exploitation is possible: Action input authorization checks may be bypassed, allowing configured restrictions to be circumvented
- Additional dependency: The resulting impact depends on the permissions and integrations available to the Scaffolder backend
Why this happens
The underlying flaw is an authorization enforcement failure in the handling of scaffolder action inputs. The backend does not consistently ensure that requested actions remain within the restrictions configured for the template or execution context, allowing an authenticated user to influence an unauthorized operation. This aligns primarily with CWE-284, Improper Access Control, and is also related to CWE-178, Improper Handling of Case Sensitivity, where inconsistent interpretation or comparison of authorization values can contribute to bypass conditions.
The underlying flaw is an authorization enforcement failure in the handling of scaffolder action inputs. The backend does not consistently ensure that requested actions remain within the restrictions configured for the template or execution context, allowing an authenticated user to influence an unauthorized operation. This aligns primarily with CWE-284, Improper Access Control, and is also related to CWE-178, Improper Handling of Case Sensitivity, where inconsistent interpretation or comparison of authorization values can contribute to bypass conditions.
Potential impact
- An attacker may invoke scaffolder actions that should be restricted
- Unauthorized repository reads, writes, or other source-control operations could occur
- Repository contents or project configuration may be modified
- Exposed integration credentials could be used beyond their intended scope
- Downstream builds, deployments, or supply-chain workflows could be affected
- An attacker may invoke scaffolder actions that should be restricted
- Unauthorized repository reads, writes, or other source-control operations could occur
- Repository contents or project configuration may be modified
- Exposed integration credentials could be used beyond their intended scope
- Downstream builds, deployments, or supply-chain workflows could be affected
General mitigation guidance
Mitigation generally focuses on enforcing authorization at the action
execution boundary rather than trusting template declarations or user-supplied
inputs alone.
Common defensive patterns include:
- Applying explicit allowlists for actions and validating them server-side
- Binding authorization decisions to the authenticated identity and intended template
- Using canonical, unambiguous comparisons for action names and related inputs
- Separating template authorship privileges from template execution privileges
- Limiting source-control credentials to the minimum required repositories and operations
- Avoiding broad shared credentials and preferring short-lived, narrowly scoped identities
- Treating template and action configuration as security-sensitive policy
- Requiring review or approval for operations that modify protected resources
Mitigation generally focuses on enforcing authorization at the action
execution boundary rather than trusting template declarations or user-supplied
inputs alone.
Common defensive patterns include:
- Applying explicit allowlists for actions and validating them server-side
- Binding authorization decisions to the authenticated identity and intended template
- Using canonical, unambiguous comparisons for action names and related inputs
- Separating template authorship privileges from template execution privileges
- Limiting source-control credentials to the minimum required repositories and operations
- Avoiding broad shared credentials and preferring short-lived, narrowly scoped identities
- Treating template and action configuration as security-sensitive policy
- Requiring review or approval for operations that modify protected resources
How teams detect issues like this
Detection can combine:
- Static analysis for authorization checks that occur only during template parsing or configuration loading
- Code review of every path from user-controlled scaffolder inputs to action dispatch
- Tests that attempt restricted actions through alternate input representations and execution paths
- Audit logging of template identity, user identity, selected actions, authorization decisions, and target repositories
- Alerts for unexpected repository access, writes, or action usage by the Scaffolder service identity
- Policy checks requiring server-side action allowlists and least-privilege integration scopes
Automated security review tools may help identify missing authorization checks,
inconsistent comparisons, and calls to privileged integrations without
corresponding policy enforcement.
Detection can combine:
- Static analysis for authorization checks that occur only during template parsing or configuration loading
- Code review of every path from user-controlled scaffolder inputs to action dispatch
- Tests that attempt restricted actions through alternate input representations and execution paths
- Audit logging of template identity, user identity, selected actions, authorization decisions, and target repositories
- Alerts for unexpected repository access, writes, or action usage by the Scaffolder service identity
- Policy checks requiring server-side action allowlists and least-privilege integration scopes
Automated security review tools may help identify missing authorization checks,
inconsistent comparisons, and calls to privileged integrations without
corresponding policy enforcement.
