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Medium

Fastify: Incorrect Content-Type parsing can lead to CSRF attack

  • Disclosed: 21.11.2022
  • Updated: 11.10.2026 10:22

Impact

The attacker can use the incorrect Content-Type to bypass the Pre-Flight checking of fetch. fetch() requests with Content-Type’s essence as "application/x-www-form-urlencoded", "multipart/form-data", or "text/plain", could potentially be used to invoke routes that only accepts application/json content type, thus bypassing any CORS protection, and therefore they could lead to a Cross-Site Request Forgery attack.

Patches

For 4.x users, please update to at least 4.10.2 For 3.x users, please update to at least 3.29.4

Workarounds

Implement Cross-Site Request Forgery protection using @fastify/csrf.

References

Check out the HackerOne report: https://hackerone.com/reports/1763832.

For more information

Fastify security policy

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
npm package fastify >= 4.0.0, < 4.10.2, >= 3.0.0, < 3.29.4 4.10.2, 3.29.4

References

CVSS score 4.2/10
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Weakness (CWE)
CWE-352
Platform
npm
Package
fastify
Disclosed
21.11.2022
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-3fjj-p79j-c9hh - CC BY 4.0

Vulnerability history: fastify

All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (16) in the archive
Total entries
16
First → latest
07.2018 09.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 8
  • Medium 7
  • Low 1

Disclosures per year

Severity:
  1. fastify vulnerable to request body replacement via an async validation result collision
    High · 8.1 CVE-2026-84504 < 5.12.2 5.12.2
  2. fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers
    High · 7.5 CVE-2026-76169 >= 4.0.0, < 5.12.2 5.12.2
  3. fastify vulnerable to request validation bypass via skipped boolean false schemas
    High · 7.5 CVE-2026-84469 < 5.12.2 5.12.2
  4. fastify vulnerable to header validation bypass via incomplete schema case normalization
    High · 7.5 CVE-2026-84428 < 5.12.2 5.12.2
  5. Fastify's Content-Type header tab character allows body validation bypass
    High · 7.5 CVE-2026-25223 < 5.7.2 5.7.2
  6. Fastify vulnerable to invalid content-type parsing, which could lead to validation bypass
    High · 7.5 CVE-2025-32442 >= 5.0.0, < 5.3.2, >= 4.29.0, < 4.29.1 5.3.2, 4.29.1
  7. Fastify: Incorrect Content-Type parsing can lead to CSRF attack this entry
    Medium · 4.2 CVE-2022-41919 >= 4.0.0, < 4.10.2, >= 3.0.0, < 3.29.4 4.10.2, 3.29.4
  8. fastify vulnerable to denial of service via malicious Content-Type
    High · 7.5 CVE-2022-39288 >= 4.0.0, < 4.8.1 4.8.1
  9. Denial of Service vulnerability with large JSON payloads in fastify
    High · 7.5 CVE-2018-3711 < 0.38.0 0.38.0

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