This is a configuration bypass vulnerability that enables arbitrary code execution. The @backstage/plugin-techdocs-node package uses an allowlist to filter dangerous MkDocs configuration keys during the documentation build process. A gap in this allowlist allows attackers to craft an mkdocs.yml that causes arbitrary Python code execution, completely bypassing TechDocs' security controls.
A path traversal vulnerability in the TechDocs local generator allows attackers to read arbitrary files from the host filesystem when Backstage is configured with techdocs.generator.runIn: local. When processing documentation from untrusted sources, symlinks within the docs directory are followed by MkDocs during the build process. File contents are embedded into generated HTML and exposed to users who can view the documentation.
When TechDocs is configured with runIn: local, a malicious actor who can submit or modify a repository's mkdocs.yml file can execute arbitrary Python code on the TechDocs build server via MkDocs hooks configuration.
A malicious actor with the ability to register entities in the Software Catalog is able to write files to arbitrary paths on the techdocs backend host instance when techdocs.publisher.type is set to local.