CVE-2026-106499

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.

The @backstage/plugin-catalog-backend package in Backstage before 3.9.1 inconsistently enforces allowed location types during catalog processing. Under certain configurations, the backend could process location types that were not intended to be allowed, potentially leading to unintended file access on the backend host.

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.

Cloud storage catalog providers in Backstage before 1.54.6 did not sufficiently validate object paths. A principal able to create or rename objects in a configured Azure Blob Storage or AWS S3 catalog source could cause catalog descriptors to be read from outside the intended storage boundary, limited to locations reachable with the backend's configured credentials.

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.

The @backstage/plugin-kubernetes-backend package in Backstage before 0.21.10 is affected by an unsupported catalog cluster authentication mode in the Kubernetes backend. Deployments using catalog cluster discovery may be affected when catalog contributors can create or modify kubernetes-cluster Resource entities. With the required endpoint permissions and pod RBAC, the backend can use its local in-cluster identity, potentially exposing Kubernetes resources readable by that identity. The credential is used only with the local in-cluster API endpoint and is not sent to the catalog-supplied endpoint.

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.