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.
Fixes and workarounds
Fix
@backstage/plugin-catalog-backend (npm): OSV reports a fixed version 3.9.2. Check the advisory for supported release branches.
Source: OSV GHSA-w658-mh9p-ww8fFix
@backstage/plugin-catalog-backend (npm): OSV reports a fixed version 4.0.2. Check the advisory for supported release branches.
Source: OSV GHSA-w658-mh9p-ww8fAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| backstage backstage |
< 3.9.2 (affected) >= 4.0.0, < 4.0.2 (affected) |
CNA: GitHub_M |
@backstage/plugin-catalog-backend@backstage/plugin-catalog-backend
npm |
≥ 0; < 3.9.2 (affected, semver); OSV events: introduced 0; fixed 3.9.2Source events (semver)Other versions: unaffected |
OSV GHSA-w658-mh9p-ww8f |
@backstage/plugin-catalog-backend@backstage/plugin-catalog-backend
npm |
≥ 4.0.0; < 4.0.2 (affected, semver); OSV events: introduced 4.0.0; fixed 4.0.2Source events (semver)Other versions: unaffected |
OSV GHSA-w658-mh9p-ww8f |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 6.5 medium |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/backstage/backstage/security/advisories/GHSA-w658-mh9p-ww8fCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/backstage/backstage/commit/3214dc8f15d4a08a2fd07a72a8fe4d00aeac0db4CNA: GitHub_M · x_refsource_MISC
- https://github.com/backstage/backstage/commit/737ff1c719dbd5a97f375b7f1db6d61416618419CNA: GitHub_M · x_refsource_MISC
- https://github.com/backstage/backstage/releases/tag/v1.54.10CNA: GitHub_M · x_refsource_MISC
- https://github.com/backstage/backstage/releases/tag/v1.56.1CNA: GitHub_M · x_refsource_MISC
- https://github.com/advisories/GHSA-w658-mh9p-ww8fOSV / GitHub Security Advisories · advisory
- https://osv.dev/vulnerability/GHSA-w658-mh9p-ww8fOSV / GitHub Security Advisories · osv
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