CVE-2026-106558: Backstage: Improper validation of TechDocs MkDocs configuration

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-07 · updated 2026-10-13
Weakness: CWE-502

Description

Backstage is an open framework for building developer portals. Prior to 1.14.8, 1.15.6, and 2.0.1, the @backstage/plugin-techdocs-node package improperly validated mapping-style markdown_extensions configuration. An authenticated attacker who can register or influence an SCM-backed documentation source may bypass TechDocs sanitization and cause Python objects to be imported and instantiated in the generator runtime, leading to arbitrary code execution. Earlier fixes in versions 1.14.6 and 1.15.4 did not fully address the supported mapping representation of markdown_extensions. Impact is greatest when documentation generation runs with backend credentials, filesystem access, or internal network access. This issue is fixed in versions 1.14.8, 1.15.6, and 2.0.1.

Affected products

backstage: before 1.50.7; from 1.51.1 before 1.54.8; from 1.55.1 before 1.55.2; 1.51.0, 1.51.0-next0, 1.51.0-next1, 1.51.0-next2, 1.51.0-next3, 1.55.0 (+3) — fixed in 1.50.7, 1.54.8, 1.55.2
Linuxfoundation Backstage Plugin-Techdocs-Node: before 1.14.8; from 1.15.0 before 1.15.6; from 2.0.0 before 2.0.1 — fixed in 1.14.8, 1.15.6, 2.0.1

How to fix

Upgrade to a fixed version: backstage 1.50.7, 1.54.8, 1.55.2; Linuxfoundation Backstage Plugin-Techdocs-Node 1.14.8, 1.15.6, 2.0.1. Check the vendor advisory for mitigations.

References

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