CVE-2026-252237.5HighCWE-436

CVE-2026-25223: Fastify's Content-Type header tab character allows body validation bypass

fastify

Vendor fix available · Affected: fastify · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.9%probability of exploitation in the next 30 days

59th percentile

050100

Higher than 59% of scored CVEs

7.5HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

fastify · fastify< 5.7.2

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Interpretation Conflict · Input Validation and Logic
Vendor: fastify
Published: February 2026
Band: Unlikely (under 1%), February 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-25223 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.