CVE-2026-29186
TechDocs Mkdocs Configuration Key Enables Arbitrary Code Execution
Impact
### Impact 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. ### Patches Patched in `@backstage/plugin-techdocs-node` version 1.14.3 ### Workarounds If users cannot upgrade immediately: 1. Use Docker mode with restricted access: Configure TechDocs with `runIn: docker` instead of `runIn: local`. This provides container isolation, though it does not fully mitigate the risk. 2. Restrict repository access: Limit who can modify `mkdocs.yml` files in repositories that TechDocs processes. Only allow trusted contributors. 3. Manual review: Implement PR review requirements for changes to `mkdocs.yml` files to detect malicious hooks configurations before they are merged. 4. Downgrade MkDocs: Use MkDocs < 1.4.0 (e.g., 1.3.1) which does not support hooks. Note: This may limit access to newer MkDocs features. Note: Building documentation in CI/CD pipelines using `@techdocs/cli` does not mitigate this vulnerability, as the CLI uses the same vulnerable `@backstage/plugin-techdocs-node` package. ### Resources [MkDocs Hooks Documentation](https://www.mkdocs.org/user-guide/configuration/#hooks) [MkDocs 1.4 Release Notes](https://www.mkdocs.org/about/release-notes/#version-14-2022-09-27) [TechDocs Architecture](https://backstage.io/docs/features/techdocs/architecture)
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @backstage/plugin-techdocs-node | <= 1.14.2 | 1.14.3 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Linuxfoundation | Backstage Plugin-Techdocs-Node | before 1.14.3 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/backstage/backstage/security/advisories/GHSA-928r-fm4v-mvrw
- https://access.redhat.com/errata/RHSA-2026:13826
- https://access.redhat.com/errata/RHSA-2026:9742
- https://access.redhat.com/security/cve/CVE-2026-29186
- https://bugzilla.redhat.com/show_bug.cgi?id=2445480
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-29186.json
- https://github.com/advisories/GHSA-928r-fm4v-mvrw
- https://backstage.io/docs/features/techdocs/architecture
- https://www.mkdocs.org/about/release-notes/#version-14-2022-09-27
- https://www.mkdocs.org/user-guide/configuration/#hooks
- https://nvd.nist.gov/vuln/detail/CVE-2026-29186