[backstage-goalie]

This PR contains the following updates:

Package	Change	Age	Confidence
@backstage/plugin-proxy-backend (source)	0.6.17 → 0.6.18

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Backstage: Inconsistent credential enforcement for overlapping proxy routes

CVE-2026-106456 / GHSA-472h-9c5j-prrr

More information

Details

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.

Severity

• CVSS Score: 4.8 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

backstage/backstage (@​backstage/plugin-proxy-backend)

v0.6.18

Compare Source

Patch Changes

• 736d84e: Use locale-insensitive Unicode casing for consistent string handling across environments.
• 42580a2: Improved request path handling in the proxy-backend.
• 9df9292: Ensure HTTP proxy requests consistently apply their configured credential requirements.
• Updated dependencies
  • @​backstage/backend-plugin-api@1.10.1
  • @​backstage/plugin-proxy-node@0.1.19

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