CVE-2026-106456

MEDIUM 4.8

Backstage: Inconsistent credential enforcement for overlapping proxy routes

CVSS Score

4.8

EPSS Score

0.0%

EPSS Percentile

0th

Backstage is an open framework for building developer portals. From 0.5.0 until 0.6.18, the @backstage/plugin-proxy-backend package is affected by inconsistent credential enforcement for overlapping proxy routes. 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. This issue is fixed in version 0.6.18.

CWE	CWE-863
Vendor	backstage
Product	backstage
Published	Oct 6, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

backstage / backstage

>= 1.28.0, < 1.55.0

@backstage / plugin-proxy-backend

>= 0.5.0, < 0.6.18

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/backstage/backstage/security/advisories/GHSA-472h-9c5j-prrr github.com: https://github.com/backstage/backstage/commit/9df92923ac32558bb80edeceafd8de780c44e218 github.com: https://github.com/backstage/backstage/releases/tag/v1.55.0