Backstage: Improper input validation in proxy-backend

{
  "id": "4f6405f5dd6b90c90b1e7a5633a188843a21912da899b5053db3484d58870096",
  "url": "https://osv.dev/vulnerability/GHSA-9ghw-48h5-v2w5",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Backstage: Improper input validation in proxy-backend",
    "summary": "### 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.",
    "evidence": "osv:GHSA-9ghw-48h5-v2w5",
    "products": [
      {
        "name": {
          "value": "@backstage/plugin-proxy-backend",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.6.17",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "GHSA-9ghw-48h5-v2w5",
      "aliases": [
        "CVE-2026-106491",
        "GHSA-9ghw-48h5-v2w5"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0.6.17"
                }
              ]
            }
          ],
          "package": {
            "name": "@backstage/plugin-proxy-backend",
            "purl": "pkg:npm/%40backstage/plugin-proxy-backend",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-9ghw-48h5-v2w5/GHSA-9ghw-48h5-v2w5.json"
          }
        }
      ],
      "modified": "2026-10-07T18:15:11.766501419Z",
      "provider": "osv",
      "references": [
        "https://github.com/backstage/backstage/security/advisories/GHSA-9ghw-48h5-v2w5",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-106491",
        "https://github.com/backstage/backstage/commit/233287d0ce3133e41549bf92a7470c940a41753c",
        "https://github.com/backstage/backstage",
        "https://github.com/backstage/backstage/releases/tag/v1.54.6"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-20",
          "CWE-22"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": "2026-10-06T21:17:18Z",
        "github_reviewed_at": "2026-10-07T17:59:49Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-106491",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 97157,
  "published_at": "2026-10-07T17:59:49+00:00"
}