CVE-2026-106503: @backstage Plugin-Scaffolder-Backend

High severity, CVSS 8.1. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• @backstage Plugin-Scaffolder-Backend: before 3.3.1 (fixed in 3.3.1); from 3.4.0, before 3.4.1 (fixed in 3.4.1); from 4.0.0, before 4.0.3 (fixed in 4.0.3); from 4.0.4, before 4.1.0 (fixed in 4.1.0)
• Backstage Backstage: before 1.49.6 (fixed in 1.49.6); from 1.50.0-next.0, before 1.50.5 (fixed in 1.50.5); from 1.51.0-next.0, before 1.54.6 (fixed in 1.54.6)

Published 2026-10-06. Last modified 2026-10-09.