Backstage is an open framework for building developer portals. 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, and write files outside the workspace via archive extraction (tar/zip) containing malicious symlinks. This affects any Backstage deployment where users can create or execute Scaffolder templates. This vulnerability is fixed in `@backstage/backend-defaults` versions 0.12.2, 0.13.2, 0.14.1, and 0.15.0; `@backstage/plugin-scaffolder-backend` versions 2.2.2, 3.0.2, and 3.1.1; and `@backstage/plugin-scaffolder-node` versions 0.11.2 and 0.12.3. Users should upgrade to these versions or later. Some workarounds are available. Follow the recommendation in the Backstage Threat Model to limit access to creating and updating templates, restrict who can create and execute Scaffolder templates using the permissions framework, audit existing templates for symlink usage, and/or run Backstage in a containerized environment with limited filesystem access.

Affected: npm: @backstage/backend-defaults, npm: @backstage/plugin-scaffolder-backend, npm: @backstage/plugin-scaffolder-node

### Impact

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:

1. **Read arbitrary files** via the `debug:log` action by creating a symlink pointing to sensitive files (e.g., `/etc/passwd`, configuration files, secrets) 2. **Delete arbitrary files** via the `fs:delete` action by creating symlinks pointing outside the workspace 3. **Write files outside the workspace** via archive extraction (tar/zip) containing malicious symlinks

This affects any Backstage deployment where users can create or execute Scaffolder templates.

### Patches

This vulnerability is fixed in the following package versions:

- `@backstage/backend-defaults` version 0.12.2, 0.13.2, 0.14.1, 0.15.0 - `@backstage/plugin-scaffolder-backend` version 2.2.2, 3.0.2, 3.1.1 - `@backstage/plugin-scaffolder-node` version 0.11.2, 0.12.3

Users should upgrade to these versions or later.

### Workarounds

- Follow the recommendation in the [Backstage Threat Model](https://backstage.io/docs/overview/threat-model#scaffolder) to limit access to creating and updating templates - Restrict who can create and execute Scaffolder templates using the permissions framework - Audit existing templates for symlink usage - Run Backstage in a containerized environment with limited filesystem access

### References

- [CWE-59: Improper Link Resolution Before File Access](http…

jsonpath: jsonpath: Prototype Pollution vulnerability in the value function multer: Multer: Denial of Service via dropped file upload connections multer: Multer: Denial of Service via malformed requests multer: Multer: Denial of Service via malformed requests backstage/backend-defaults: backstage/plugin-scaffolder-backend: backstage/plugin-scaffolder-node: possible symlink path traversal in scaffolder actions @backstage/plugin-techdocs-node: @backstage/plugin-techdocs-node vulnerable to arbitrary code execution via MkDocs hooks axios: Axios affected by Denial of Service via __proto__ Key in mergeConfig fast-xml-parser: fast-xml-parser: Cross-Site Scripting (XSS) due to improper DOCTYPE entity handling fast-xml-parser: fast-xml-parser: Denial of Service via unlimited XML entity expansion rollup: Rollup: Remote Code Execution via Path Traversal Vulnerability fast-xml-parser: fast-xml-parser: Stack overflow leads to Denial of Service google.golang.org/grpc/grpc-go: google.golang.org/grpc/authz: gRPC-Go: Authorization bypass due to improper HTTP/2 path validation