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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-29186 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Detection & 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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-29186 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-29186. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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…
| 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?
O3 Security finds CVE-2026-29186 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.