Vulnerability · Published Jun 23, 2026 · Assigned by VulnCheck

CVE-2026-56762Hono - Missing Cookie Name Validation in setCookie()

Medium 5.3

In plain English

A medium-severity improper input validation 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 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.4%top 63.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Hono before 4.12.12 does not validate cookie names on the write path in the setCookie(), serialize(), and serializeSigned() functions, allowing invalid characters such as control characters (e.g. \r or \n) when an application passes a user-controlled cookie name. This can produce malformed Set-Cookie header values. In modern runtimes such as Node.js and Cloudflare Workers, such invalid header values are rejected and cause a runtime error before the response is sent, so header injection or response splitting could not be reproduced; the issue primarily affects correctness and robustness, resulting in runtime errors (availability) rather than confirmed header injection.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	hono	4.12.12	GHSA-26pp-8wgv-hjvm

Affected products (as reported)

Vendor	Product	Versions
Hono	Hono	0 – before 4.12.12

Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

GitHub Security Advisory (GHSA-26pp-8wgv-hjvm) vendor-advisory
VulnCheck Advisory: Hono - Missing Cookie Name Validation in setCookie() third-party-advisory