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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.","state":0,"publishedAt":"2026-10-06T21:17:15.903+00:00","modifiedAt":"2026-10-27T20:51:42.72+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","score":4.8,"severity":"MEDIUM"},{"system":"CVSS 3.1 · nvd@nist.gov · Primary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","score":6.5,"severity":"MEDIUM"}],"references":["https://github.com/backstage/backstage/commit/9df92923ac32558bb80edeceafd8de780c44e218","https://github.com/backstage/backstage/releases/tag/v1.55.0","https://github.com/backstage/backstage/security/advisories/GHSA-472h-9c5j-prrr"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-106456","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-863"],"productCriteria":["cpe:2.3:a:linuxfoundation:backstage\\/plugin-proxy-backend:*:*:*:*:*:node.js:*:*","cpe:2.3:a:linuxfoundation:backstage:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-10-06T21:17:15.903","lastModified":"2026-10-27T20:51:42.720"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-106456","identifiers":["CVE-2026-106456"]},"retained":false,"historicalAffected":[]},{"revision":"24e972ba184b453dbf8116deae585d21","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-472h-9c5j-prrr","aliases":["CVE-2026-106456"],"title":"Backstage: Inconsistent credential enforcement for overlapping proxy routes","description":"### Impact\n\nAn 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.\n\nExploitation requires this specific overlapping route configuration. The resulting confidentiality and integrity impact depends on the capabilities exposed by the nested upstream.\n\n### Patches\n\nUpgrade `@backstage/plugin-proxy-backend` to version `0.6.18` or later. The fixed package is available in [Backstage v1.55.0](https://github.com/backstage/backstage/releases/tag/v1.55.0).\n\n### Workarounds\n\n- Avoid nesting a credential-protected proxy path below a path configured with `dangerously-allow-unauthenticated`.\n- Apply the same credential requirement to overlapping proxy paths.\n- Restrict direct network access to the Backstage backend until the patched package is deployed.","state":0,"publishedAt":"2026-10-07T20:25:13+00:00","modifiedAt":"2026-10-07T20:30:07.2255335+00:00","affected":[{"ecosystem":"npm","name":"@backstage/plugin-proxy-backend","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0.5.0"},{"kind":"fixed","version":"0.6.18"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"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"],"sourceUrl":"https://github.com/advisories/GHSA-472h-9c5j-prrr","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-472h-9c5j-prrr","identifiers":["GHSA-472h-9c5j-prrr","CVE-2026-106456"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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