CVE-2026-88064: Backstage

High severity, CVSS 8.8. EPSS: 1.2% chance of exploitation in the next 30 days.

Backstage is an open framework for building developer portals. Prior to 1.14.6 and from 1.15.0 until 1.15.4, the @backstage/plugin-techdocs-node package insufficiently validates mkdocs.yml supplied by an authenticated user who can register or modify a TechDocs source. Unsafe Python YAML tags, markdown_extensions names and configuration, theme options, and extra_templates values can reach the documentation generator and cause unintended code execution. The resulting impact is limited to the files, credentials, network access, and other resources available to the TechDocs backend or build container. This issue is fixed in versions 1.14.6 and 1.15.4.

Affected products

• Backstage Backstage: before 1.14.6 (fixed in 1.14.6); from 1.15.0, before 1.15.4 (fixed in 1.15.4)

Published 2026-09-16. Last modified 2026-09-30.