{"id":"CVE-2026-106491","aliases":["EUVD-2026-94010","GHSA-9ghw-48h5-v2w5"],"status":"published","title":"Backstage: Improper input validation in proxy-backend","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.","severity":{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00275,"percentile":0.20084,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20","CWE-22"],"published":"2026-10-06T20:45:08Z","modified":"2026-10-28T02:30:34Z","fixes":[{"ecosystem":"npm","package":"@backstage/plugin-proxy-backend","fixed_in":["0.6.17"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@backstage/plugin-proxy-backend","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.6.17"}]}]},{"source":"osv","ecosystem":"npm","package":"@backstage/plugin-proxy-backend","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.6.17"}]}]}],"products":[{"vendor":"@backstage","product":"plugin-proxy-backend"},{"vendor":"backstage","product":"backstage"},{"vendor":"linuxfoundation","product":"backstage"},{"vendor":"linuxfoundation","product":"backstage\\/plugin-proxy-backend"}],"references":[{"url":"https://github.com/backstage/backstage/security/advisories/GHSA-9ghw-48h5-v2w5","tags":["x_refsource_CONFIRM","Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://github.com/backstage/backstage/commit/233287d0ce3133e41549bf92a7470c940a41753c","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/backstage/backstage/releases/tag/v1.54.6","tags":["x_refsource_MISC","Patch","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-106491","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-9ghw-48h5-v2w5"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/106xxx/CVE-2026-106491.json","tags":["advisory"]},{"url":"https://github.com/backstage/backstage","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-106491","title":"Backstage: Improper input validation in proxy-backend","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.","status":"published","published":"2026-10-06T20:45:08.067Z","modified":"2026-10-07T17:52:11.914Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-20","CWE-22"],"updated_at":"2026-11-02T14:20:04.463704Z"}],"euvd":[{"id":"EUVD-2026-94010","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.","status":"published","published":"2026-10-06T20:45:08Z","modified":"2026-10-07T17:52:11Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T17:27:34.815018Z"}],"ghsa":[{"id":"GHSA-9ghw-48h5-v2w5","title":"Backstage: Improper input validation in proxy-backend","description":"### Impact\n\nAn 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.\n\n### Patches\n\nPatched in `@backstage/plugin-proxy-backend` version `0.6.17`\n\n### Workarounds\n\n- Deploy a reverse proxy or WAF in front of Backstage that normalizes request paths before they reach the backend.","status":"published","published":"2026-10-07T17:59:49Z","modified":"2026-10-07T17:59:49Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-20","CWE-22"],"updated_at":"2026-11-02T14:41:28.013673Z"}],"nvd":[{"id":"CVE-2026-106491","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.","status":"published","published":"2026-10-06T21:17:18.073Z","modified":"2026-10-22T14:10:06.117Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-20","CWE-22"],"updated_at":"2026-11-02T14:12:54.809359Z"}],"osv":[{"id":"CVE-2026-106491","title":"Backstage: Improper input validation in proxy-backend","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.","status":"published","published":"2026-10-06T20:45:08.067Z","modified":"2026-10-28T02:30:34.875611601Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-20","CWE-22"],"updated_at":"2026-11-02T15:44:54.583213Z"},{"id":"GHSA-9ghw-48h5-v2w5","title":"Backstage: Improper input validation in proxy-backend","description":"### Impact\n\nAn 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.\n\n### Patches\n\nPatched in `@backstage/plugin-proxy-backend` version `0.6.17`\n\n### Workarounds\n\n- Deploy a reverse proxy or WAF in front of Backstage that normalizes request paths before they reach the backend.","status":"published","published":"2026-10-07T17:59:49Z","modified":"2026-10-07T18:15:11.766501419Z","cvss":[{"version":"3.1","score":6.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-20","CWE-22"],"updated_at":"2026-11-02T15:46:43.875515Z"}]}}