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High

fastify vulnerable to denial of service via malicious Content-Type

  • Disclosed: 11.10.2022
  • Updated: 11.10.2026 10:22

Impact

An attacker can send an invalid Content-Type header that can cause the application to crash, leading to a possible Denial of Service attack. Only the v4.x line is affected.

(This was updated: upon a close inspection, v3.x is not affected after all).

Patches

Yes, update to > v4.8.0.

Workarounds

You can reject the malicious content types before the body parser enters in action.

js
  const badNames = Object.getOwnPropertyNames({}.__proto__)
  fastify.addHook('onRequest', async (req, reply) => {
    for (const badName of badNames) {
      if (req.headers['content-type'].indexOf(badName) > -1) {
        reply.code(415)
        throw new Error('Content type not supported')
      }
    }
  })

References

See the HackerOne report #1715536

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, < 4.8.1 4.8.1

References

CVSS score 7.5/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE)
CWE-754
Platform
npm
Package
fastify
Disclosed
11.10.2022
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-455w-c45v-86rg - 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 vulnerable to denial of service via malicious Content-Type this entry
    High · 7.5 CVE-2022-39288 >= 4.0.0, < 4.8.1 4.8.1
  8. 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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