CVE-2026-106501

Backstage before version 4.1.0 in the @backstage/plugin-scaffolder-backend package could expose secret-derived values in Scaffolder task logs. Deployments that configure sensitive scaffolder.defaultEnvironment.secrets and allow an attacker to create or modify Scaffolder templates are affected. A template author could cause secret-derived values used during template iteration to be persisted and exposed to users who can access the resulting task logs.

Backstage before version 3.9.1 in the @backstage/plugin-catalog-backend package has inconsistent catalog property permission evaluation. In deployments that use affected value-based catalog permission conditions as a confidentiality boundary, an authenticated user could receive catalog entity data that policy authors intended to restrict.

Backstage before version 0.17.8 in the @backstage/backend-defaults package has improper input validation in cloud storage url readers. An attacker with write access to a cloud storage bucket used by Backstage could craft object names that could collide with protected files in the output directory. In certain deployment configurations, this could lead to content injection.

Backstage before version 0.6.17 in the @backstage/plugin-proxy-backend package has improper input validation in proxy-backend. An authenticated Backstage user could craft a request URL that causes the proxy-backend to forward the request to a path outside the configured base path on the target server. This is limited to target servers already configured as proxy endpoints and requires Backstage authentication by default.

Backstage before version 2.2.4 in the @backstage/plugin-techdocs-backend package has improper input validation in techdocs static content requests. When using the Azure Blob Storage provider, an authenticated Backstage user may be able to read restricted TechDocs content when entity-level permissions are enabled. Deployments that intentionally disable the default backend authentication policy may have broader exposure.

Backstage before version 2.2.4 in the @backstage/plugin-techdocs-backend package has improper authorization enforcement for techdocs static content. An authenticated user with access to one TechDocs documentation site could craft a URL able to read documentation belonging to a different entity. This only affects deployments using the external TechDocs builder with an external storage provider (S3, GCS, etc.) and the permission framework enabled. Instances that do not use the permission framework are unaffected, since TechDocs content is visible to all authenticated users by design.

Backstage before version 0.8.7 in the @backstage/plugin-catalog-backend-module-gitlab package has improper authorization in gitlab organizational user ingestion. Deployments that enable GitLab organization event ingestion and rely on scoped catalog users as an access boundary may admit an unintended catalog identity. Depending on sign-in and permission configuration, this may allow unauthorized access with the permissions of a standard authenticated user.

Backstage prior to 1.54.6 does not consistently enforce credential boundaries in scaffolder source-control actions. An authenticated user could cause an affected action to fall back to broader integration credentials and perform operations with more access than intended. This issue is fixed in 1.54.6 when operators also enable scaffolder.requireScmUserCredentials after upgrading.

Backstage before version 0.29.2 has a vulnerability in the experimental dynamic client registration and client ID metadata document features in @backstage/plugin-auth-backend. Full-string glob matching can be bypassed, allowing an attacker-controlled redirect URI with a trusted hostname suffix in its path to pass the allowlist and receive an OAuth authorization code after a victim completes the flow. These features are experimental and disabled by default.

Backstage is vulnerable to symlink-based path traversal attacks in Scaffolder actions and archive extraction utilities. An attacker with access to create and execute Scaffolder templates can read, delete, or write files outside the workspace.