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Vulnerability record · CVE-2026-25223 · published 3 February 2026

CVE-2026-25223: Fastify interpretation conflict vulnerability

Fastify · Fastify

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.

7.5 CVSS 3.1 High EPSS 0.82% · top 44.6% CWE-436 · Interpretation conflictCWE-179 · CWE-179
7.5CVSS 3.1 base score
0.82%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
12References
15 Jul 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://fastify.dev/docs/latest/Reference/Validation-and-Serialization ProductTechnical Description
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
https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821 Patch
https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq MitigationVendor Advisory
https://hackerone.com/reports/3464114 Permissions Required
https://access.redhat.com/errata/RHSA-2026:10184
https://access.redhat.com/errata/RHSA-2026:5807
https://access.redhat.com/errata/RHSA-2026:6192
https://access.redhat.com/security/cve/CVE-2026-25223
https://bugzilla.redhat.com/show_bug.cgi?id=2436560
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25223.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-25223), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.