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.
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-29186.json
https://github.com/backstage/backstage/security/advisories/GHSA-928r-fm4v-mvrw
https://bugzilla.redhat.com/show_bug.cgi?id=2445480
https://access.redhat.com/security/cve/CVE-2026-29186