{"id":"GHSA-qmw8-3v4g-gwj4","summary":"Prefix escape","details":"### Impact\n\nBy crafting a specific URL, it is possible to escape the prefix of the proxied backend service.\nIf the base url of the proxied server is `/pub/`, a user expect that accessing `/priv` on the target service would not be possible. Unfortunately, it is.\n\n[CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N)\n\n### Patches\n\nA patch have been submitted by Corey Farrell git@cfware.com, the reporter.\nAll releases after v4.0.2 include the fix.\n\n### Workarounds\n\nThere are no workaround available.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [fastify-reply-from](https://github.com/fastify/fastify-reply-from)\n* Email us at [hello@matteocollina.com](mailto:hello@matteocollina.com)","aliases":["CVE-2021-21321"],"modified":"2026-07-08T06:29:17.757441041Z","published":"2021-03-03T01:52:05Z","database_specific":{"severity":"CRITICAL","github_reviewed":true,"github_reviewed_at":"2021-03-02T03:32:13Z","nvd_published_at":"2021-03-02T04:15:00Z","cwe_ids":["CWE-20"]},"references":[{"type":"WEB","url":"https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21321"},{"type":"WEB","url":"https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889"},{"type":"WEB","url":"https://www.npmjs.com/package/fastify-reply-from"}],"affected":[{"package":{"name":"fastify-reply-from","ecosystem":"npm","purl":"pkg:npm/fastify-reply-from"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.0.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/03/GHSA-qmw8-3v4g-gwj4/GHSA-qmw8-3v4g-gwj4.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N"}]}