CVE-2026-106509 Backstage: Improper validation of MkDocs theme configuration in TechDocs
Attackers with repository write access can execute arbitrary code during documentation builds via malicious MkDocs theme configurations in Backstage TechDocs.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-106509?
CVE-2026-106509 is a high-severity code injection vulnerability in Linuxfoundation Backstage, published on 6 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Backstage is an open framework for building developer portals. Prior to 1.14.6, the @backstage/plugin-techdocs-node package is affected by improper validation of mkdocs theme configuration in techdocs. When TechDocs is configured to build documentation locally or in a container, a user with write access to a registered repository can include configuration values in mkdocs.yml that cause arbitrary code execution during the documentation build process. This issue is fixed in versions 1.14.6 and 1.15.4.
Which versions are affected by CVE-2026-106509?
2 open source packages ship an affected version, including @backstage/plugin-techdocs-node. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
@backstage/plugin-techdocs-node npm | All versions | 1.15.4 |
@backstage/plugin-techdocs-node npm | All versions | 1.15.4 |
Products include Linuxfoundation Backstage, Linuxfoundation Backstage Plugin-Techdocs-Node.
How do I fix CVE-2026-106509?
Upgrade @backstage/plugin-techdocs-node to 1.15.4 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-106509 being exploited?
There is no known exploitation of CVE-2026-106509 in the wild and no public exploit code.
Other vulnerabilities in Linuxfoundation Backstage
- CVE-2026-106501 Backstage: Sensitive information exposure in Scaffolder
- CVE-2026-106558 Backstage: Improper validation of TechDocs MkDocs configuration
- CVE-2026-88064 Backstage: Improper input validation in TechDocs MkDocs configuration
- CVE-2026-106459 Backstage: Improper input validation in Sentry scaffolder actions
- CVE-2026-106486 Backstage: Improper filesystem validation in Bitbucket pull-request scaffolder actions
Sources
Also known as GHSA-8w7q-29mw-gf5c.