In short
- CVE-2026-106491 is a MEDIUM (CVSS 6.4) vulnerability affecting backstage (linuxfoundation), backstage/plugin-proxy-backend (linuxfoundation), @backstage/plugin-proxy-backend.
- Chance of exploitation in the next 30 days (EPSS): 0.27%, higher than 19.9% of all vulnerabilities.
- Fix: update to 1.54.6, 0.6.17 or later.
Description
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.
NVD description
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-backend. 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. This issue is fixed in version 0.6.17.
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