CVE-2026-88064: Backstage: Improper input validation in TechDocs MkDocs configuration

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-16 · updated 2026-10-14
Weakness: CWE-20

Description

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: before 1.14.6; from 1.15.0 before 1.15.4 — fixed in 1.14.6, 1.15.4
Linuxfoundation Backstage Plugin-Techdocs-Node: before 1.14.6; from 1.15.0 before 1.15.4 — fixed in 1.14.6, 1.15.4

How to fix

Upgrade to a fixed version: backstage 1.14.6, 1.15.4; Linuxfoundation Backstage Plugin-Techdocs-Node 1.14.6, 1.15.4. Check the vendor advisory for mitigations.

References

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