{"cve":"CVE-2021-21321","nvd":{"published":"2021-03-02T04:15:12.487","modified":"2026-06-17T03:35:17.573","status":"Modified","description":"fastify-reply-from is an npm package which is a fastify plugin to forward the current http request to another server. In fastify-reply-from before version 4.0.2, by crafting a specific URL, it is possible to escape the prefix of the proxied backend service. If the base url of the proxied server is \"/pub/\", a user expect that accessing \"/priv\" on the target service would not be possible. In affected versions, it is possible. This is fixed in version 4.0.2.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","score":10.0},"cwes":["CWE-20"],"references":["https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889","https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4","https://www.npmjs.com/package/fastify-reply-from","https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889","https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4"],"products":["fastify-reply-from_project:fastify-reply-from"],"source":"nvd","synced_at":"2026-10-19T21:15:50.279857260+00:00"},"epss":{"cve":"CVE-2021-21321","score":0.01821,"percentile":0.78757,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-qmw8-3v4g-gwj4","url":"https://osv.dev/vulnerability/GHSA-qmw8-3v4g-gwj4","summary":"Prefix escape","modified":"2026-07-08T06:29:17.757441041Z","packages":[{"ecosystem":"npm","name":"fastify-reply-from","purl":"pkg:npm/fastify-reply-from","ranges":["<4.0.2"],"fixed":["4.0.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}