Advisories for Npm/@Backstage/Backend-Defaults package

An authenticated user could invoke actions that an operator had excluded through action configuration. Existing action permissions and downstream authorization remain enforced.

An external service credential configured with access restrictions (e.g., read-only) could bypass those restrictions by routing requests through plugin delegation paths. This could allow a restricted service to perform operations beyond its intended scope, including write operations on plugins it was restricted to read-only access for.

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.

Catalog entity providers for Azure Blob Storage and AWS S3 did not sufficiently validate storage object paths, which could allow catalog descriptors to be read from outside the intended storage boundary. Access is limited to locations reachable by the backend's configured credentials.

Multiple Scaffolder actions and archive extraction utilities were vulnerable to symlink-based path traversal attacks. An attacker with access to create and execute Scaffolder templates could exploit symlinks to: Read arbitrary files via the debug:log action by creating a symlink pointing to sensitive files (e.g., /etc/passwd, configuration files, secrets) Delete arbitrary files via the fs:delete action by creating symlinks pointing outside the workspace Write files outside the workspace via archive extraction …

The FetchUrlReader component, used by the catalog and other plugins to fetch content from URLs, followed HTTP redirects automatically. This allowed an attacker who controls a host listed in backend.reading.allow to redirect requests to internal or sensitive URLs that are not on the allowlist, bypassing the URL allowlist security control. This is a Server-Side Request Forgery (SSRF) vulnerability that could allow access to internal resources, but it does not allow …