PT-2026-6281 · Fastify · Fastify

Highmcollina + 1 · Published 2026-02-02 · Updated 2026-02-04 · CVE-2026-25223

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Name of the Vulnerable Software and Affected Versions Fastify versions prior to 5.7.2

Description Fastify is a web framework for Node.js. A validation bypass exists where request body validation schemas specified by Content-Type can be circumvented. Appending a tab character (t) followed by arbitrary content to the Content-Type header allows attackers to bypass body validation while the server processes the body as the original content type. The affected API endpoint receives requests with a Content-Type header, and the vulnerable parameter is the Content-Type header itself.

Recommendations Update to version 5.7.2 or later.

Exploit

Fix

Weakness Enumeration

CWE-436

Related Identifiers

CVE-2026-25223

GHSA-JX2C-RXCM-JVMQ

Affected Products

Fastify

References · 14

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/25xxx/CVE-2026-25223.json · Exploit
• https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821 · Patch
• https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2026-25223 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-jx2c-rxcm-jvmq · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-25223 · Security Note
• https://github.com/fastify/fastify · Note
• https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125 · Note
• https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272 · Note
• https://fastify.dev/docs/latest/Reference/Validation-and-Serialization · Note
• https://t.me/CVEtracker/43658 · Telegram Post
• https://hackerone.com/reports/3464114 · Note
• https://twitter.com/VulmonFeeds/status/2018873334444835051 · Twitter Post
• https://twitter.com/CVEnew/status/2018806728037421292 · Twitter Post