Medium · CVSS 6.5CVE-2026-115923

Backstage catalog rules can be bypassed for URL locations using encoded path segmentsCVE-2026-115923

Answer in brief

CVE-2026-115923 records a Medium severity (CVSS 6.5) vulnerability in Backstage catalog rules can be bypassed for URL locations using encoded path segments. The current sources do not mark it as known exploited. The current feed maps backstage/backstage (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 26, 2026Updated Oct 26, 2026Source checked Oct 26, 2026First seen by HOL Oct 26, 2026Material review Oct 26, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps backstage/backstage (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
backstage/backstagegeneric	<3.9.2 \|\| >=4.0.0 <4.0.2	3.9.2, 4.0.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for backstage/backstage.
Review the reported fix. Update backstage/backstage to 3.9.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 26, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.