Fastify vulnerable to invalid content-type parsing, which could lead to validation bypass
Impact
In applications that specify different validation strategies for different content types, it's possible to bypass the validation by providing a slightly altered content type such as with different casing or altered whitespacing before ;.
Users using the the following pattern are affected:
fastify.post('/', {
handler(request, reply) {
reply.code(200).send(request.body)
},
schema: {
body: {
content: {
'application/json': {
schema: {
type: 'object',
properties: {
'foo': {
type: 'string',
}
},
required: ['foo']
}
},
}
}
}
})User using the following pattern are not affected:
fastify.post('/', {
handler(request, reply) {
reply.code(200).send(request.body)
},
schema: {
body: {
type: 'object',
properties: {
'foo': {
type: 'string',
}
},
required: ['foo']
}
}
})Patches
This was patched in v5.3.1, but unfortunately it did not cover all problems. This has been fully patched in v5.3.2. Version v4.9.0 was also affected by this issue. This has been fully patched in v4.9.1.
Workarounds
Do not specify multiple content types in the schema.
References
Are there any links users can visit to find out more?
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | fastify | >= 5.0.0, < 5.3.2, >= 4.29.0, < 4.29.1 | 5.3.2, 4.29.1 |
References
- https://github.com/fastify/fastify/security/advisories/GHSA-247c-9743-5963
- https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc
- https://nvd.nist.gov/vuln/detail/CVE-2025-32442
- https://nvd.nist.gov/vuln/detail/CVE-2026-33806
- https://github.com/fastify/fastify/commit/f3d2bcb3963cd570a582e5d39aab01a9ae692fe4
- https://cna.openjsf.org/security-advisories.html
- https://github.com/fastify/fastify
- https://github.com/fastify/fastify/releases/tag/v5.8.5
- https://github.com/fastify/fastify/commit/436da4c06dfbbb8c24adee3a64de0c51e4f47418
- https://hackerone.com/reports/3087928
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-1287- Platform
- npm
- Package
fastify- Disclosed
- 18.04.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-247c-9743-5963 - CC BY 4.0
OSV / GitHub Advisory Database - GHSA-mg2h-6x62-wpwc - 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.
- 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
- 2018: 1
- 2019: 0
- 2020: 1
- 2021: 0
- 2022: 2
- 2023: 0
- 2024: 0
- 2025: 1
- 2026: 11
-
Fastify vulnerable to invalid content-type parsing, which could lead to validation bypass this entry
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