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Vulnerability · Published Oct 26, 2026 · Assigned by GitHub_M

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

Medium 6.5

In plain English

A medium-severity path traversal in backstage from backstage. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.3%top 75.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@backstage/plugin-catalog-backend3.9.2GHSA-w658-mh9p-ww8f
npm@backstage/plugin-catalog-backend4.0.2GHSA-w658-mh9p-ww8f

Affected products (as reported)

VendorProductVersions
backstage backstage < 3.9.2>= 4.0.0, < 4.0.2

Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

References