What’s Vulnerable › Vulnerabilities

CVE-2021-29624: Lack of protection against cookie tossing attacks in fastify-csrf

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-19 · updated 2026-06-17
• Weakness: CWE-565

Description

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 products

• fastify-csrf: before 3.1.0 — fixed in 3.1.0

How to fix

Upgrade to a fixed version: fastify-csrf 3.1.0. Check the vendor advisory for mitigations.

References

• https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html
• https://github.com/fastify/csrf/pull/2
• https://github.com/fastify/fastify-csrf/pull/51
• https://github.com/fastify/fastify-csrf/releases/tag/v3.1.0
• https://github.com/fastify/fastify-csrf/security/advisories/GHSA-rc4q-9m69-gqp8
• https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdf
• https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html
• https://github.com/fastify/csrf/pull/2
• https://github.com/fastify/fastify-csrf/pull/51
• https://github.com/fastify/fastify-csrf/releases/tag/v3.1.0
• https://github.com/fastify/fastify-csrf/security/advisories/GHSA-rc4q-9m69-gqp8
• https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdf

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