Summary
@backstage/plugin-catalog-backend matches URL-type locations against catalog.rules location patterns using the raw URL string submitted by the user, while URL readers resolve that same string in canonical form when fetching the location's content. A URL can therefore be crafted so that it appears to belong to a trusted location scope during rule evaluation, but is fetched from a different scope.
Details
When a deployment restricts catalog kinds to trusted URL prefixes using catalog.rules location patterns, DefaultCatalogRulesEnforcer applies glob matching directly to the raw location.target string. The URL readers used for ingestion resolve the same target in canonical form, including normalizing percent-encoded dot segments. A registered location such as https://<host>/trusted/%2e%2e/attacker/repo/blob/main/catalog-info.yaml matches a https://<host>/trusted/ pattern as a raw string, but resolves to and is fetched from https://<host>/attacker/repo/... when its content is read.
An authenticated user with permission to register catalog locations (catalog.location.create) can use this to have an entity from an untrusted source admitted as if it originated from a trusted location scope.
Impact
The crossed boundary is the operator-configured catalog ingestion policy: entity content from outside the trusted location scope is ingested as if it were within it. Downstream consequences depend on deployment configuration, for example actions taken with integration credentials by processors or scaffolder when acting on the ingested entity. The assessment of this report found no basis for impact claims beyond the ingestion policy boundary itself.
Patches
This is fixed in @backstage/plugin-catalog-backend 3.9.2 (Backstage release 1.54.10) and 4.0.2 (Backstage release 1.56.1). Version 4.0.1 as published is not fixed.
Workarounds
No complete workaround is available for deployments that rely on URL location patterns to restrict catalog kinds. Restricting location registration permissions reduces exposure.
Impact
An authenticated Backstage user could craft a catalog entity with placeholder directives that reference resources outside the entity's source repository. Under certain configurations, this could allow access to data not intended to be available to the user.
Patches
Patched in @backstage/plugin-catalog-backend version 3.9.1
Workarounds
If you're not able to update immediately:
- Limit the scope of integration credentials (e.g., GitHub tokens) to only the repositories that Backstage needs to access.
Backstage is an open framework for building developer portals. Prior to 3.9.1, the @backstage/plugin-catalog-backend package is affected by 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. This issue is fixed in version 3.9.1.
Impact
Under certain configurations, the catalog backend could process location types that were not intended to be allowed, potentially leading to unintended file access on the backend host.
Patches
Patched in @backstage/plugin-catalog-backend version 3.9.1
Workarounds
No practical workarounds are available. Upgrade to the patched version.