Vulnerability in Fastify
CVE-2026-25223
Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.009 (58.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.009 · change: +0.001
Affected products
- Fastify — versions < 5.7.2
Weakness classification (CWE)
References
- https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq (Mitigation, Vendor Advisory)
- https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821 (Patch)
- https://hackerone.com/reports/3464114 (Permissions Required)
- https://fastify.dev/docs/latest/Reference/Validation-and-Serialization (Technical Description, Product)
- https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125 (Product)
- https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272 (Product)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-25223?
- CVE-2026-25223 is a high-severity vulnerability in Fastify, classified under CWE-436. CVSS score: 7.5/10. Published 2026-02-03.
- How severe is CVE-2026-25223?
- High severity. CVSS v3 base score is 7.5 out of 10.