CVE-2026-29186 — @backstage/plugin-techdoc…
HIGHCVE-2026-29186 is a high-severity (CVSS 7.7) CWE-74 vulnerability in @backstage/plugin-techdocs-node. A fix is available for @backstage/plugin-techdocs-node — see the affected versions and patch details below.
TechDocs Mkdocs Configuration Key Enables Arbitrary Code Execution
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-29186.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@backstage/plugin-techdocs-nodenpmDescription
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:
- Use Docker mode with restricted access: Configure TechDocs with
runIn: dockerinstead ofrunIn: local. This provides container isolation, though it does not fully mitigate the risk. - Restrict repository access: Limit who can modify
mkdocs.ymlfiles in repositories that TechDocs processes. Only allow trusted contributors. - Manual review: Implement PR review requirements for changes to
mkdocs.ymlfiles to detect malicious hooks configurations before they are merged. - 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 MkDocs 1.4 Release Notes TechDocs Architecture
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @backstage/plugin-techdocs-node | all versions | 1.14.3npm install @backstage/plugin-techdocs-node@1.14.3 |
Affected Products
backstage plugin-techdocs-nodelinuxfoundationDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @backstage/plugin-techdocs-node, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @backstage/plugin-techdocs-node to 1.14.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-29186 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
To exploit this issue, an attacker needs commit access to a repository that Backstage is configured to track and build in order to introduce a malicious mkdocs.yml file into the TechDocs build pipeline. Additionally, an attacker can execute arbitrary Python code but the payload is confined by the permissions granted…
To mitigate this issue, enable docker isolation by updating the Backstage configuration to use 'runIn: docker' instead of 'runIn: local', confining the arbitrary Python code execution to a containerized environment. Additionally, limit commit access to repositories tracked by Backstage to trusted contributors only, and enforce mandatory pull request (PR) reviews for any modifications made to the mkdocs.yml file.Source: Red Hat security advisory for CVE-2026-29186 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Developer Hub 1.8 | rhdh/rhdh-hub-rhel9:1776784286 | RHSA-2026:9742 |
| Red Hat Developer Hub 1.9 | rhdh/rhdh-hub-rhel9:1777903262 | RHSA-2026:13826 |
Frequently Asked Questions
Is CVE-2026-29186 in your dependencies?
Find it across npm, including transitive dependencies.