Lack of protection against cookie tossing attacks in fastify-csrf

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2021-29624: 0.83% estimated exploitation activity in the next 30 days; percentile 57.59 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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-SiteRequestForgeryPreventionCheatSheet.html 2. https://owasp.org/www-pdf-archive/DavidJohansson-DoubleDefeatofDouble-SubmitCookie.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 Email us at hello@matteocollina.com

Published by the source

17 May 2021, 20:53 UTC

Last modified by the source

8 Jul 2026, 06:28 UTC

Source last checked

26 Oct 2026, 12:16 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rc4q-9m69-gqp8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-rc4q-9m69-gqp8

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# Patch Next advisory brief: CVE-2021-29624

Advisory: Lack of protection against cookie tossing attacks in fastify-csrf
IDs: CVE-2021-29624, GHSA-rc4q-9m69-gqp8
Record: https://patchnext.com/advisories/cve-2021-29624 (revision 2, source checked 26 Oct 2026, 12:16 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fastify-csrf 3.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm fastify-csrf: affected < 3.1.0; fixed in 3.1.0

## Suggested inspection (read-only)
- `npm ls fastify-csrf --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on fastify-csrf.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-rc4q-9m69-gqp8 (OSV record GHSA-rc4q-9m69-gqp8 lists affected ranges: npm fastify-csrf >=0 <3.1.0 (fixed))
- Verified: https://github.com/advisories/GHSA-rc4q-9m69-gqp8 (GitHub-reviewed advisory GHSA-rc4q-9m69-gqp8 lists affected ranges: npm fastify-csrf >=0 <3.1.0)

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