Backstage: Improper input validation in proxy-backend
### Impact An authenticated Backstage user could craft a request URL that causes the proxy-backend to forward the request to a path outside the configured base path on the target server. This is limited to target servers already configured as proxy endpoints and requires Backstage authentication by default. ### Patches Patched in `@backstage/plugin-proxy-backend` version `0.6.17` ### Workarounds - Deploy a reverse proxy or WAF in front of Backstage that normalizes request paths before they reach the backend.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-106491US | — | — | ||
Backstage is an open framework for building developer portals. Prior to 0.6.17, the @backstage/plugin-proxy-backend package is affected by improper input validation in proxy-backen… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/backstage/backstagePACKAGE
- https://github.com/backstage/backstage/commit/233287d0ce3133e41549bf92a7470c940a41753cWEB
- https://github.com/backstage/backstage/releases/tag/v1.54.6WEB
- https://github.com/backstage/backstage/security/advisories/GHSA-9ghw-48h5-v2w5WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-106491ADVISORY
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