CVE-2026-115923: Backstage catalog rules can be bypassed for URL locations using encoded path segments
Backstage is an open framework for building developer portals. Prior to 3.9.2 and from 4.0.0 until 4.0.2, DefaultCatalogRulesEnforcer in @backstage/plugin-catalog-backend compares the raw location.target URL against catalog.rules, while URL readers canonicalize the same URL before fetching it. An authenticated user with catalog.location.create permission can use percent-encoded path segments to make an untrusted URL match a trusted location pattern even though the canonical URL resolves outside that scope. This admits entity content from an untrusted source as trusted, while further downstream consequences depend on deployment configuration. This issue is fixed in versions 3.9.2 and 4.0.2.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
@backstage/plugin-catalog-backendto a version that resolves this vulnerability.Fixed in 3.9.2 - Upgrade
Upgrade
@backstage/plugin-catalog-backendto a version that resolves this vulnerability.Fixed in 4.0.2
Event History
Frequently Asked Questions
Who can exploit this issue?
An authenticated user who has the catalog.location.create permission can exploit it. The attacker must be able to submit a URL location whose raw URL matches a trusted catalog.rules pattern while percent-encoded path segments cause its canonicalized URL to resolve outside that trusted scope.
Which versions are affected and which versions contain the fix?
Versions before 3.9.2 are affected, as are versions from 4.0.0 through 4.0.1. The issue is fixed in 3.9.2 and 4.0.2.
What is the practical impact of a successful bypass?
The bypass can cause entity content from an untrusted source to be admitted as trusted by the catalog. Any further impact depends on the deployment's downstream configuration and handling of that entity content.