CVE-2026-126356

Hono: `validator('form')` skips validation for `multipart/form-data` requests with extra parameters

Published Nov 12, 2026 CVSS 3.1 · 5.3 Medium EPSS n/a KEV · Not listed
Description
Hono is a Web application framework that provides support for any JavaScript runtime. From 4.5.1 until 4.13.16, validator('form') uses a strict whole-header pattern that fails to recognize multipart/form-data when its Content-Type includes another legal parameter or extra whitespace after a semicolon. The validation callback receives an empty object even though c.req.parseBody() or c.req.formData() can still parse and expose all submitted fields to the handler. An unauthenticated client can therefore bypass allow-list or required-field checks when the application relies on the form validator and its callback accepts an empty object. application/x-www-form-urlencoded requests are not affected. This issue is fixed in version 4.13.16.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4h7h-rv7c-7m2v Hono: `validator('form')` skips validation for `multipart/form-data` requests with extra parameters
History
Type Values Removed Values Added
Description Hono is a Web application framework that provides support for any JavaScript runtime. From 4.5.1 until 4.13.16, validator('form') uses a strict whole-header pattern that fails to recognize multipart/form-data when its Content-Type includes another legal parameter or extra whitespace after a semicolon. The validation callback receives an empty object even though c.req.parseBody() or c.req.formData() can still parse and expose all submitted fields to the handler. An unauthenticated client can therefore bypass allow-list or required-field checks when the application relies on the form validator and its callback accepts an empty object. application/x-www-form-urlencoded requests are not affected. This issue is fixed in version 4.13.16.
Title Hono: `validator('form')` skips validation for `multipart/form-data` requests with extra parameters
Weaknesses CWE-1471
CWE-20
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

Subscriptions

No data.

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 13, 2026, 12:36 AM
Reserved
Nov 10, 2026, 9:12 PM
Status
Deferred
Published
Nov 13, 2026, 12:20 AM
Modified
Nov 13, 2026, 2:18 AM