Summary
Improper input validation in Backstage Sentry scaffolder actions may allow an authenticated internal user to make the backend send requests to unintended destinations.
If the backend can reach attacker-selected or sensitive endpoints, the issue may disclose Sentry integration credentials or other response data. The resulting impact depends on network access and the privileges associated with the configured token.
Improper input validation in Backstage Sentry scaffolder actions may allow an authenticated internal user to make the backend send requests to unintended destinations.
If the backend can reach attacker-selected or sensitive endpoints, the issue may disclose Sentry integration credentials or other response data. The resulting impact depends on network access and the privileges associated with the configured token.
Affected context
The issue affects Backstage deployments using vulnerable versions of the
@backstage/plugin-scaffolder-backend-module-sentry package and enabling the
affected Sentry scaffolder actions. Risk is higher when authenticated internal
users can execute those actions, the backend has broad outbound network
reachability, or Sentry tokens have permissions beyond the minimum required.
The issue affects Backstage deployments using vulnerable versions of the
@backstage/plugin-scaffolder-backend-module-sentry package and enabling the
affected Sentry scaffolder actions. Risk is higher when authenticated internal
users can execute those actions, the backend has broad outbound network
reachability, or Sentry tokens have permissions beyond the minimum required.
Exploit preconditions
- Attack surface: Backstage Sentry scaffolder actions
- Required access: Authenticated internal-user access with permission to execute the affected actions
- Trigger point: Processing attacker-influenced destination or request parameters within a scaffolder action
- Environmental requirement: The Backstage backend must be able to reach the unintended destination
- Why exploitation is possible: Input validation does not sufficiently constrain outbound request targets, allowing the server to act as a request intermediary and potentially expose integration credentials
- Attack surface: Backstage Sentry scaffolder actions
- Required access: Authenticated internal-user access with permission to execute the affected actions
- Trigger point: Processing attacker-influenced destination or request parameters within a scaffolder action
- Environmental requirement: The Backstage backend must be able to reach the unintended destination
- Why exploitation is possible: Input validation does not sufficiently constrain outbound request targets, allowing the server to act as a request intermediary and potentially expose integration credentials
Why this happens
The underlying bug is insufficient validation and restriction of user-influenced destinations in server-side request logic. When a backend accepts destination-related input without enforcing an appropriate allowlist, URL policy, or network-boundary check, an authorized user may cause the server to issue requests outside the intended Sentry integration scope.
This behavior maps primarily to CWE-918: Server-Side Request Forgery (SSRF). The resulting disclosure of credentials or response content also relates to CWE-200: Exposure of Sensitive Information to an Unauthorized Actor.
The underlying bug is insufficient validation and restriction of user-influenced destinations in server-side request logic. When a backend accepts destination-related input without enforcing an appropriate allowlist, URL policy, or network-boundary check, an authorized user may cause the server to issue requests outside the intended Sentry integration scope.
This behavior maps primarily to CWE-918: Server-Side Request Forgery (SSRF). The resulting disclosure of credentials or response content also relates to CWE-200: Exposure of Sensitive Information to an Unauthorized Actor.
Potential impact
- The backend may contact internal, private, or otherwise unintended network destinations
- Sentry integration credentials or sensitive response data could be disclosed
- An attacker could make requests using the privileges of the Backstage backend
- Internal services may be probed or accessed if network controls permit it
- Misuse of a highly privileged Sentry token could increase downstream impact
- The backend may contact internal, private, or otherwise unintended network destinations
- Sentry integration credentials or sensitive response data could be disclosed
- An attacker could make requests using the privileges of the Backstage backend
- Internal services may be probed or accessed if network controls permit it
- Misuse of a highly privileged Sentry token could increase downstream impact
General mitigation guidance
Mitigation generally focuses on reducing trust in action parameters and constraining all server-side outbound requests.
Common defensive patterns include:
- Restricting destinations through explicit host, scheme, port, and network-range allowlists
- Rejecting loopback, link-local, private, metadata-service, and other non-approved address ranges
- Validating destinations after resolution and accounting for redirects and DNS rebinding
- Keeping Sentry credentials server-side and preventing their inclusion in arbitrary responses
- Applying least privilege and narrow scopes to configured integration tokens
- Limiting which users and workflows can execute network-capable scaffolder actions
- Enforcing egress network policies so the backend can reach only required services
- Returning minimal, sanitized action results rather than forwarding raw upstream responses
Mitigation generally focuses on reducing trust in action parameters and constraining all server-side outbound requests.
Common defensive patterns include:
- Restricting destinations through explicit host, scheme, port, and network-range allowlists
- Rejecting loopback, link-local, private, metadata-service, and other non-approved address ranges
- Validating destinations after resolution and accounting for redirects and DNS rebinding
- Keeping Sentry credentials server-side and preventing their inclusion in arbitrary responses
- Applying least privilege and narrow scopes to configured integration tokens
- Limiting which users and workflows can execute network-capable scaffolder actions
- Enforcing egress network policies so the backend can reach only required services
- Returning minimal, sanitized action results rather than forwarding raw upstream responses
How teams detect issues like this
Detection can combine source analysis, runtime monitoring, and policy enforcement:
- Use static analysis to identify outbound HTTP clients that consume action or template parameters
- Review URL parsing, redirect handling, DNS resolution, and private-address filtering
- Flag scaffolder actions that construct requests from user-controlled strings
- Monitor backend egress for unexpected destinations, cloud metadata access, private-network requests, or unusual Sentry-token usage
- Enforce repository and CI policies requiring approved destination allowlists for network-capable actions
- Review authorization policies to ensure only appropriate users can invoke actions with outbound network access
- Automated code-review and dependency-analysis tools may help identify SSRF patterns and vulnerable package usage
Detection can combine source analysis, runtime monitoring, and policy enforcement:
- Use static analysis to identify outbound HTTP clients that consume action or template parameters
- Review URL parsing, redirect handling, DNS resolution, and private-address filtering
- Flag scaffolder actions that construct requests from user-controlled strings
- Monitor backend egress for unexpected destinations, cloud metadata access, private-network requests, or unusual Sentry-token usage
- Enforce repository and CI policies requiring approved destination allowlists for network-capable actions
- Review authorization policies to ensure only appropriate users can invoke actions with outbound network access
- Automated code-review and dependency-analysis tools may help identify SSRF patterns and vulnerable package usage
