CVE-2026-115923

Backstage catalog rules can be bypassed for URL locations using encoded path segments

Published Oct 26, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-w658-mh9p-ww8f Backstage catalog rules can be bypassed for URL locations using encoded path segments
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Backstage
Backstage backstage
Vendors & Products Backstage
Backstage backstage
Type Values Removed Values Added
Description 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.
Title Backstage catalog rules can be bypassed for URL locations using encoded path segments
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 2, 2026, 5:52 PM
Reserved
Oct 23, 2026, 8:21 PM
Status
Awaiting Analysis
Published
Oct 26, 2026, 6:17 PM
Modified
Nov 2, 2026, 6:18 PM