CVE-2026-106498: Backstage: Improper URL validation in catalog entity placeholder resolution

Severity: high (CVSS 7.7 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 2026-10-16
Weakness: CWE-863

Description

Backstage is an open framework for building developer portals. Prior to 3.5.1, 3.6.2, 3.7.2, 3.8.2 and 3.9.1, the @backstage/plugin-catalog-backend package is affected by improper url validation in catalog entity placeholder resolution. An authenticated Backstage user could craft a catalog entity with placeholder directives that reference resources outside the entity's source repository. Under certain configurations, this could allow access to data not intended to be available to the user. This issue is fixed in versions 3.5.1, 3.6.2, 3.7.2, 3.8.2 and 3.9.1.

Affected products

backstage: before 1.49.6; from 1.50.0 before 1.50.5; from 1.51.0 before 1.51.3; from 1.52.0 before 1.53.2; from 1.54.0 before 1.54.6 — fixed in 1.49.6, 1.50.5, 1.51.3, 1.53.2, 1.54.6
Linuxfoundation Backstage Plugin-Catalog-Backend: before 3.5.1; from 3.6.0 before 3.6.2; from 3.7.0 before 3.7.2; from 3.8.0 before 3.8.2; from 3.9.0 before 3.9.1 — fixed in 3.5.1, 3.6.2, 3.7.2, 3.8.2, 3.9.1

How to fix

Upgrade to a fixed version: backstage 1.49.6, 1.50.5, 1.51.3, 1.53.2; Linuxfoundation Backstage Plugin-Catalog-Backend 3.5.1, 3.6.2, 3.7.2, 3.8.2. Check the vendor advisory for mitigations.

References

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