# CVE-2026-106503: Backstage Scaffolder Backend authorization bypass in action input validation

Source: https://junglewise.ai/threats/cve-2026-106503-backstage-is-an-open-framework-for-building-developer-portals  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-06. Updated: 2026-10-06  
License: CC BY 4.0 with a link back

CVE-2026-106503 · Severity: high · CVSS 8.1 · Published 2026-10-06

Backstage is an open framework for building developer portals where authenticated users can run templated scaffold actions. A flaw in the Scaffolder Backend plugin allows authenticated users to bypass restrictions on which actions they are permitted to use by manipulating action input validation. An attacker could exploit this to access repositories and source control systems they shouldn't have permission to use.

Technologies: [Backstage Plugin-Scaffolder-Backend](https://junglewise.ai/threats/technologies/plugin-scaffolder-backend), [@backstage/plugin-scaffolder-backend (npm)](https://junglewise.ai/threats/technologies/backstage-plugin-scaffolder-backend). Vendors: [Backstage](https://junglewise.ai/threats/vendors/backstage), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-106503 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-106503 being exploited in the wild.

**How severe is CVE-2026-106503?** High severity, with a CVSS score of 8.1, published 6 October 2026.

**Which products and versions are affected?** Backstage Plugin-Scaffolder-Backend prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0; @backstage/plugin-scaffolder-backend (npm) SEMVER:introduced=0,fixed=3.3.1.

**Is there a fix for CVE-2026-106503?** Yes. @backstage/plugin-scaffolder-backend (npm): upgrade to 3.3.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-106503 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-106503?** Check whether you run Backstage Plugin-Scaffolder-Backend or @backstage/plugin-scaffolder-backend (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @backstage/plugin-scaffolder-backend (npm): upgrade to 3.3.1 or later

  ```sh
  npm install @backstage/plugin-scaffolder-backend@3.3.1
  ```


## Technical details

The @backstage/plugin-scaffolder-backend package fails to properly validate action input values against configured permission policies, allowing authenticated users to circumvent action restrictions. The vulnerability requires authentication and is triggered when a user with access to affected Scaffolder templates supplies crafted input that bypasses permission matching logic. An attacker gains the ability to execute restricted scaffold actions and access associated integration credentials.

## Affected products

- Backstage plugin-scaffolder-backend prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0

## Identifiers

- CVE-2026-106503
- GHSA-hmp2-4m7g-22cv

## Timeline

- 2026-10-06: disclosed

## References

- [https://github.com/backstage/backstage/commit/11c1384c0649b8ab26391c6a4e4f34b80ab0d188](https://github.com/backstage/backstage/commit/11c1384c0649b8ab26391c6a4e4f34b80ab0d188)
- [https://github.com/backstage/backstage/commit/a91ed72d540e80b62a73b39bb1563ff5018d52d1](https://github.com/backstage/backstage/commit/a91ed72d540e80b62a73b39bb1563ff5018d52d1)

## Related threats

- [Backstage scaffolder task list input validation vulnerability](https://junglewise.ai/threats/cve-2026-106506-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage scaffolder-backend sensitive information exposure in task logs](https://junglewise.ai/threats/cve-2026-106504-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage plugin-scaffolder-backend credential exposure in task events](https://junglewise.ai/threats/cve-2026-106502-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage plugin-scaffolder-backend sensitive information exposure](https://junglewise.ai/threats/cve-2026-106501-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage plugin-scaffolder-backend improper task state validation](https://junglewise.ai/threats/cve-2026-106500-backstage-is-an-open-framework-for-building-developer-portals)