high CVSS 7.7

CVE-2026-29186·Python vulnerability

Backstage is an open framework for building developer portals. Prior to version 1.14.3, 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. This issue has been patched in version 1.14.3.

Severity
high
Software
Python
Fixed in
1.14.3
Published
2026-03-07

Affected versions

Until: 1.14.3

Fixed in: 1.14.3

How to fix this CVE

Update Backstage and the @backstage/plugin-techdocs-node package to version 1.14.3 or later to apply security patches that close the MkDocs configuration allowlist bypass. Organizations should immediately audit any TechDocs instances and review recent documentation builds for suspicious activity, as the vulnerability allows attackers to execute arbitrary Python code during the build process by crafting malicious mkdocs.yml files.

sudo dnf update python3

Defensia detects this vulnerability

How to check if you are affected

  1. Run `python3 --version` to confirm the Python interpreter version installed on the system
  2. Check for Backstage installation: `npm list @backstage/plugin-techdocs-node` or examine package-lock.json for versions below 1.14.3
  3. Review TechDocs build logs (typically in Backstage logs directory) for unexpected Python execution or error messages during mkdocs.yml parsing
  4. Verify the patch: `npm list @backstage/plugin-techdocs-node` should show version 1.14.3 or higher after remediation

FAQ

What is CVE-2026-29186?

CVE-2026-29186 is a configuration bypass vulnerability in Backstage's TechDocs plugin that exploits incomplete validation of MkDocs configuration files, allowing attackers to inject and execute arbitrary Python code during documentation builds.

Is CVE-2026-29186 being actively exploited?

No, CVE-2026-29186 is not currently listed in the CISA Known Exploited Vulnerabilities catalog and no public exploit code is available, though organizations should still prioritize patching given the severity and attack feasibility.

What versions of the @backstage/plugin-techdocs-node package are affected by CVE-2026-29186?

All versions prior to 1.14.3 are affected; version 1.14.3 and all subsequent releases include the security fix.

How do I check if my Backstage deployment is vulnerable to CVE-2026-29186?

Run `npm list @backstage/plugin-techdocs-node` in your Backstage root directory; if the version is below 1.14.3, your instance is vulnerable.

Does Defensia detect CVE-2026-29186?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If @backstage/plugin-techdocs-node is present on a monitored server, CVE-2026-29186 will appear in your dashboard with remediation steps.

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References

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