Backstage has a Possible Symlink Path Traversal in Scaffolder Actions

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 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
• OWASP Path Traversal