CVE-2023-27495
Bypass of CSRF protection in the presence of predictable userInfo
Impact
## Description The [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. `@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. As 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. ### Patches This is patched in version 6.3.0 and v4.1.0. ### Workarounds As a workaround, developers can use a random, non-predictable `userInfo` parameter for each user. ## Credits * Pedro Adão (@pedromigueladao), [Instituto Superior Técnico, University of Lisbon](https://tecnico.ulisboa.pt/) * Marco Squarcina (@lavish), [Security & Privacy Research Unit, TU Wien](https://secpriv.wien/)
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @fastify/csrf-protection | < 4.1.0 | 4.1.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Fastify | Csrf-Protection | before 4.1.0 from 5.0.0 before 6.3.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/fastify/csrf-protection/commit/be3e5761f37aa05c7c1ac8ed44499c51ecec8058
- https://github.com/fastify/csrf-protection/security/advisories/GHSA-qrgf-9gpc-vrxw
- https://www.cvedetails.com/cve/CVE-2021-29624
- https://github.com/advisories/GHSA-qrgf-9gpc-vrxw
- https://github.com/fastify/csrf-protection/security/advisories/GHSA-rc4q-9m69-gqp8
- https://nvd.nist.gov/vuln/detail/CVE-2023-27495
- https://github.com/fastify/csrf-protection/releases/tag/v4.1.0
- https://github.com/fastify/csrf-protection/releases/tag/v6.3.0