fastify-csrf is an open-source plugin helps developers protect their Fastify server against CSRF attacks. Versions of fastify-csrf prior to 3.1.0 have a "double submit" mechanism using cookies with an application deployed across multiple subdomains, e.g. "heroku"-style platform as a service. Version 3.1.0 of the fastify-csrf fixes it. the vulnerability. The user of the module would need to supply a `userInfo` when generating the CSRF token to fully implement the protection on their end. This is needed only for applications hosted on different subdomains.

Affected: npm: fastify-csrf

### Impact

Users that used fastify-csrf with the "double submit" mechanism using cookies with an application deployed across multiple subdomains, e.g. "heroku"-style platform as a service.

### Patches

Version 3.1.0 of the fastify-csrf fixes it. See https://github.com/fastify/fastify-csrf/pull/51 and https://github.com/fastify/csrf/pull/2.

The user of the module would need to supply a `userInfo` when generating the CSRF token to fully implement the protection on their end. This is needed only for applications hosted on different subdomains.

### Workarounds

None available.

### References

1. https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html 2. https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdf

### Credits

This vulnerability was found by Xhelal Likaj <xhelallikaj20@gmail.com>.

### For more information If you have any questions or comments about this advisory: * Open an issue in [fastify-csrf](https://github.com/fastify/fastify-csrf) * Email us at [hello@matteocollina.com](mailto:hello@matteocollina.com)