Backstage up to 0.6.17 @backstage/plugin-proxy-backend improper authorization

Summaryinfo

A vulnerability has been found in Backstage up to 0.6.17 and classified as critical. Affected by this issue is some unknown functionality of the component @backstage/plugin-proxy-backend. This manipulation causes improper authorization. This vulnerability appears as CVE-2026-106456. The attack may be initiated remotely. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in Backstage up to 0.6.17. Affected by this vulnerability is an unknown part of the component @backstage/plugin-proxy-backend. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-106456 since 10/06/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

Upgrading to version 0.6.18 eliminates this vulnerability.

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Productinfo

Name

• Backstage

Version

• 0.6.0
• 0.6.1
• 0.6.2
• 0.6.3
• 0.6.4
• 0.6.5
• 0.6.6
• 0.6.7
• 0.6.8
• 0.6.9
• 0.6.10
• 0.6.11
• 0.6.12
• 0.6.13
• 0.6.14
• 0.6.15
• 0.6.16
• 0.6.17

Website

• Product: https://github.com/backstage/backstage/

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