CVE-2026-115923 Backstage catalog rules can be bypassed for URL locations using encoded path segments
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-115923?
CVE-2026-115923 is a medium-severity vulnerability in backstage, published on 26 Oct 2026.
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.
Weakness: CWE-22
Which versions are affected by CVE-2026-115923?
4 open source packages ship an affected version, including @backstage/plugin-catalog-backend.
| Package | Affected | Fixed in |
|---|---|---|
@backstage/plugin-catalog-backend npm | All versions | 3.9.2 |
@backstage/plugin-catalog-backend npm | All versions | 3.9.2 |
@backstage/plugin-catalog-backend npm | From 4.0.0 | 4.0.2 |
@backstage/plugin-catalog-backend npm | From 4.0.0 | 4.0.2 |
How do I fix CVE-2026-115923?
Upgrade @backstage/plugin-catalog-backend to a fixed version for your release line: 3.9.2 or 4.0.2.
Is CVE-2026-115923 being exploited?
There is no known exploitation of CVE-2026-115923 in the wild and no public exploit code.
Sources
Also known as GHSA-w658-mh9p-ww8f.