Backstage: Inconsistent credential enforcement for overlapping proxy routes
Impact
An operator can configure overlapping proxy paths with different credential requirements. When a parent path permits unauthenticated access and a nested path requires credentials, the parent exemption can also cover requests handled by the nested proxy. An unauthenticated caller may therefore reach the nested upstream through Backstage, including with static upstream credentials configured for that proxy.
Exploitation requires this specific overlapping route configuration. The resulting confidentiality and integrity impact depends on the capabilities exposed by the nested upstream.
Patches
Upgrade @backstage/plugin-proxy-backend to version 0.6.18 or later. The fixed package is available in Backstage v1.55.0.
Workarounds
- Avoid nesting a credential-protected proxy path below a path configured with
dangerously-allow-unauthenticated. - Apply the same credential requirement to overlapping proxy paths.
- Restrict direct network access to the Backstage backend until the patched package is deployed.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @backstage/plugin-proxy-backend | >= 0.5.0, < 0.6.18 | 0.6.18 |
References
- https://github.com/backstage/backstage/security/advisories/GHSA-472h-9c5j-prrr
- https://nvd.nist.gov/vuln/detail/CVE-2026-106456
- https://github.com/backstage/backstage/commit/9df92923ac32558bb80edeceafd8de780c44e218
- https://github.com/backstage/backstage
- https://github.com/backstage/backstage/releases/tag/v1.55.0
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N- Weakness (CWE)
CWE-863- Platform
- npm
- Package
@backstage/plugin-proxy-backend- Disclosed
- 07.10.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-472h-9c5j-prrr - CC BY 4.0
Vulnerability history: @backstage/plugin-proxy-backend
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 10.2026 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
Disclosures per year
- 2026: 2
-
Backstage: Inconsistent credential enforcement for overlapping proxy routes this entry
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.