CVE-2026-56763 | Hono before 4.12.7 allows __proto__ key in parseBody with do… | CVSS 4.8 MEDIUM

Description

Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.

Metadata

CVE ID: CVE-2026-56763
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-06-22 21:55 UTC
Published: 2026-07-11 13:00 UTC
Last updated: 2026-07-11 13:00 UTC
Primary CWE: CWE-1321
Improperly Controlled Modification of Object Prototype Attri…
Vendor / Product: Hono / Hono
Sources: cve.org · NVD

Severity & Metrics

4.8 MEDIUM CVSS 3.1

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

Affected products (1)

Vendor	Product	Platform	Versions
Hono	Hono	—	0 < 4.12.7, 4.12.7

Weakness (CWE)

CWE	Source	Description
CWE-1321	cna	Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

CVSS scores (2)

Score	Severity	Version	Source	Vector
6.3	MEDIUM	4.0	cna	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
4.8	MEDIUM	3.1	cna	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

References (2)

GitHub Security Advisory (GHSA-v8w9-8mx6-g223) https://github.com/honojs/hono/security/advisories/GHSA-v8w9-8mx6-g223
VulnCheck Advisory: Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option https://www.vulncheck.com/advisories/hono-prototype-pollution-via-proto-key-in-parsebody-with-dot-option