{"id":"GHSA-qrgf-9gpc-vrxw","summary":"Bypass of CSRF protection in the presence of predictable userInfo","details":"## Description\nThe [CSRF](https://owasp.org/www-community/attacks/csrf) protection enforced by the `@fastify/csrf-protection` library in combination with `@fastify/cookie` can be bypassed from network and same-site attackers under certain conditions.\n\n`@fastify/csrf-protection` supports an optional `userInfo` parameter that binds the CSRF token to the user. This parameter has been introduced to prevent cookie-tossing attacks as a fix for [CVE-2021-29624](https://www.cvedetails.com/cve/CVE-2021-29624). Whenever `userInfo` parameter is missing, or its value can be predicted for the target user account, network and [same-site](https://canitakeyoursubdomain.name/) attackers can 1. fixate a `_csrf` cookie in the victim's browser, and 2. forge CSRF tokens that are valid for the victim's session. This allows attackers to bypass the CSRF protection mechanism.\n\nAs a fix, `@fastify/csrf-protection` starting from version 6.3.0 (and v4.1.0) includes a server-defined secret `hmacKey` that cryptographically binds the CSRF token to the value of the `_csrf` cookie and the `userInfo` parameter, making tokens non-spoofable by attackers. This protection is effective as long as the `userInfo` parameter is unique for each user.\n\n### Patches\n\nThis is patched in version 6.3.0 and v4.1.0.\n\n### Workarounds\n\nAs a workaround, developers can use a random, non-predictable `userInfo` parameter for each user.\n\n## Credits\n* Pedro Adão (@pedromigueladao), [Instituto Superior Técnico, University of Lisbon](https://tecnico.ulisboa.pt/)\n* Marco Squarcina (@lavish), [Security & Privacy Research Unit, TU Wien](https://secpriv.wien/)","aliases":["CVE-2023-27495"],"modified":"2026-09-10T03:49:57.077390149Z","published":"2023-04-20T21:18:51Z","database_specific":{"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2023-04-20T21:18:51Z","nvd_published_at":"2023-04-20T18:15:07Z","cwe_ids":["CWE-352"]},"references":[{"type":"WEB","url":"https://github.com/fastify/csrf-protection/security/advisories/GHSA-qrgf-9gpc-vrxw"},{"type":"WEB","url":"https://github.com/fastify/csrf-protection/security/advisories/GHSA-rc4q-9m69-gqp8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-27495"},{"type":"WEB","url":"https://github.com/fastify/csrf-protection/commit/be3e5761f37aa05c7c1ac8ed44499c51ecec8058"},{"type":"PACKAGE","url":"https://github.com/fastify/csrf-protection"},{"type":"WEB","url":"https://github.com/fastify/csrf-protection/releases/tag/v4.1.0"},{"type":"WEB","url":"https://github.com/fastify/csrf-protection/releases/tag/v6.3.0"},{"type":"WEB","url":"https://www.cvedetails.com/cve/CVE-2021-29624"}],"affected":[{"package":{"name":"@fastify/csrf-protection","ecosystem":"npm","purl":"pkg:npm/%40fastify/csrf-protection"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.1.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/04/GHSA-qrgf-9gpc-vrxw/GHSA-qrgf-9gpc-vrxw.json"}},{"package":{"name":"@fastify/csrf-protection","ecosystem":"npm","purl":"pkg:npm/%40fastify/csrf-protection"},"ranges":[{"type":"SEMVER","events":[{"introduced":"5.0.0"},{"fixed":"6.3.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/04/GHSA-qrgf-9gpc-vrxw/GHSA-qrgf-9gpc-vrxw.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N"}]}