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The TechDocs plugin in Backstage enables teams to publish documentation generated from Markdown files alongside their source repositories. When Backstage is configured to process and serve documentation locally using the `techdocs.publisher.type: ‘local’` option, the plugin relies on Node.js file system routines to deliver requested static assets to end users.
Under normal operation, MkDocs compiles source files into HTML and static resources within a designated build output directory. However, when handling incoming requests to the TechDocs serving endpoint, the local publisher failed to strictly enforce path sanitization and boundary checking against the base documentation root. If a static documentation bundle or path reference contains directory traversal sequences or relative symbolic references, the file resolution logic in `@backstage/plugin-techdocs-node` can follow these references outside the intended output directory.
As a result, an authenticated user who interacts with the documentation endpoint can potentially cause the backend to read and serve files from the host operating system’s broader file system, limited only by the permissions of the running Backstage Node.js process. This behavior is confined to instances using local storage; cloud-native publishers such as AWS S3, Google Cloud Storage, or Azure Blob Storage handle file retrieval via object APIs and remain unaffected by host file system traversal risks.
DailyCVE Form:
Platform: Backstage TechDocs
Version: < 1.15.4
Vulnerability: Path Traversal Exposing
Severity: Medium
date: Oct 6 2026
Prediction: Oct 6 2026
What Undercode Say: Analytics
Analysis of Configuration and Backend Logging
Check if Backstage application configuration uses the vulnerable local publisher grep -r "publisher.type: 'local'" app-config.yaml configs/ Audit installed version of the affected plugin package npm list @backstage/plugin-techdocs-node
// Example conceptual representation of insecure relative path joining
const path = require('path');
const fs = require('fs');
function serveDocFile(baseDir, requestedPath) {
// Vulnerable pattern: unsafe path resolution without boundary checks
const targetPath = path.join(baseDir, requestedPath);
return fs.readFileSync(targetPath);
}
Exploit: (Educational Purposes!)
Path traversal vulnerabilities occur when application logic fails to verify that a computed target file path remains within a restricted directory root.
In a local file publisher context, an attacker leverages input strings containing sequences like `../` to manipulate path concatenation functions (path.join). If the application does not validate the resolved path using canonicalization methods (path.resolve) and boundary conditions (startsWith), the operating system attempts to locate the file relative to parent directories rather than the documentation root.
Protection: from this CVE
- Upgrade Package: Update `@backstage/plugin-techdocs-node` to version `1.15.4` or later to apply official sanitization patches.
- Switch Publisher: Configure Backstage to use external cloud storage plugins (e.g.,
awsS3,googleGcs, orazureBlobStorage) instead oflocal. - Container Isolation: Run the Backstage backend in an isolated container environment with strictly limited file system permissions to restrict access to sensitive system files.
Impact
Successful exploitation allows authenticated users to read arbitrary host files accessible by the Backstage Node.js process user, potentially exposing configuration credentials, source code, or internal tokens.
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Sources:
Reported By: github.com
Extra Source Hub:
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