CVE-2021-29624

Name: CVE-2021-29624
Creator: NVD / NIST
Published: 2021-05-19T22:15:07.837+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.83%

Last modified Jun 17, 2026

CVE-2021-29624 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 0.83% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS Probability

0.83%

52.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Fastify	Fastify-Csrf	< 3.1.0

References

https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.htmlThird Party Advisory
https://github.com/fastify/csrf/pull/2Patch, Third Party Advisory
https://github.com/fastify/fastify-csrf/pull/51Patch, Third Party Advisory
https://github.com/fastify/fastify-csrf/releases/tag/v3.1.0Third Party Advisory
https://github.com/fastify/fastify-csrf/security/advisories/GHSA-rc4q-9m69-gqp8Patch, Third Party Advisory
https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdfThird Party Advisory
https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.htmlThird Party Advisory
https://github.com/fastify/csrf/pull/2Patch, Third Party Advisory
https://github.com/fastify/fastify-csrf/pull/51Patch, Third Party Advisory
https://github.com/fastify/fastify-csrf/releases/tag/v3.1.0Third Party Advisory
https://github.com/fastify/fastify-csrf/security/advisories/GHSA-rc4q-9m69-gqp8Patch, Third Party Advisory
https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdfThird Party Advisory

Timeline

Published: May 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29624?

How severe is CVE-2021-29624?

CVE-2021-29624 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.83% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29624?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-29624?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST