CVE-2026-106500: Backstage: Improper task state validation in Scaffolder backend

Severity: high (CVSS 8.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-06 · updated 2026-10-13
Weakness: CWE-59

Description

Backstage is an open framework for building developer portals. Prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0, the @backstage/plugin-scaffolder-backend package is affected by improper task state validation in scaffolder backend. An authenticated user with permission to create and access Scaffolder tasks may, under specific timing and deployment conditions, affect files accessible to the Backstage backend. If backend application files are writable, the confidentiality, integrity, and availability of the backend may be compromised. This issue is fixed in versions 3.3.1, 3.4.1, 4.0.3 and 4.1.0.

Affected products

backstage: before 1.49.6; from 1.50.0 before 1.50.5; from 1.51.0 before 1.54.6 — fixed in 1.49.6, 1.50.5, 1.54.6
@backstage plugin-scaffolder-backend: before 3.3.1; from 3.4.0 before 3.4.1; from 4.0.0 before 4.0.3; from 4.0.4 before 4.1.0 — fixed in 3.3.1, 3.4.1, 4.0.3, 4.1.0

How to fix

Upgrade to a fixed version: backstage 1.49.6, 1.50.5, 1.54.6; @backstage plugin-scaffolder-backend 3.3.1, 3.4.1, 4.0.3, 4.1.0. Check the vendor advisory for mitigations.

References

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