Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-106509

CVE-2026-106509HIGH

Backstage: Improper validation of MkDocs theme configuration in TechDocs

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   L   N  U  H  H  H    8.8   .0037   29.3     —

AFFECTED
  Product               Versions    Fixed
  backstage             < 1.50.5 –  —
  plugin-techdocs-node  < 1.14.6 –  —

TIMELINE
  Oct 6   Reserved by GitHub_M
  Oct 6   Published (CNA: GitHub_M)
  Oct 9   EXPLOIT PUBLISHED — CVE-2026-106509 (backstage). Public exploit reference added.
  Oct 9   RESCORED — CVE-2026-106509 (backstage). CVSS 7.7 → 8.8 (NVD).

CWE-94, CWE-1336 · CNA: GitHub_M · CVSS v3.1 · 5 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
October 6, 2026	Reserved	Reserved by GitHub_M
October 6, 2026	Published	Published (CNA: GitHub_M)
October 9, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-106509 (backstage). Public exploit reference added.
October 9, 2026	RESCORED	RESCORED — CVE-2026-106509 (backstage). CVSS 7.7 → 8.8 (NVD).

Affected

Affected products and packages — 2 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
backstage	backstage	—	< 1.50.5	—
@backstage	plugin-techdocs-node	—	< 1.14.6	—

Weaknesses

CWE-94 · CWE-1336

References (5)

https://github.com/backstage/backstage/commit/02cd7cdbb18b687446277b5602adaee7f1d53cbb [Exploit, Patch]
https://github.com/backstage/backstage/commit/a900a9953c8f7ad3ba1906d1d257725a9996cc9d [Exploit, Patch]
https://github.com/backstage/backstage/releases/tag/v1.50.5 [Release Notes]
https://github.com/backstage/backstage/releases/tag/v1.54.6 [Release Notes]
https://github.com/backstage/backstage/security/advisories/GHSA-8w7q-29mw-gf5c [Vendor Advisory, Mitigation]

Authoritative record: CVE-2026-106509 at cve.org

Vendors: backstage · @backstage

Weaknesses: CWE-94 · CWE-1336

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-106509 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.