Vulnerability · Published Jul 11, 2026 · Assigned by VulnCheck

CVE-2026-56763Hono - Prototype Pollution via proto Key in parseBody with dot Option

Medium 4.8

In plain English

A medium-severity prototype pollution in Hono from Hono. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.8Medium

Exploit odds (30 days)0.3%top 80.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	hono	4.12.7	GHSA-v8w9-8mx6-g223

Affected products (as reported)

Vendor	Product	Versions
Hono	Hono	0 – before 4.12.7

Weakness: CWE-1321 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

References

GitHub Security Advisory (GHSA-v8w9-8mx6-g223) vendor-advisory
VulnCheck Advisory: Hono - Prototype Pollution via __proto__ Key in parseBody with dot Option third-party-advisory