CVE-2026-56762 Hono - Missing Cookie Name Validation in setCookie()
Attackers can cause runtime errors and denial of service by passing invalid characters in user-controlled cookie names to the Hono web framework.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-56762?
CVE-2026-56762 is a medium-severity vulnerability in Hono, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-20
Which versions are affected by CVE-2026-56762?
2 open source packages ship an affected version, including hono.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | All versions | 4.12.12 |
hono npm | All versions | 4.12.12 |
How do I fix CVE-2026-56762?
Upgrade hono to 4.12.12 or later.
Is CVE-2026-56762 being exploited?
There is no known exploitation of CVE-2026-56762 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-NV57735, GHSA-26pp-8wgv-hjvm, MINI-87w7-2pjv-9x5p, MINI-cqrj-rf6g-v432, MINI-m6p6-3gwx-vgxf, MINI-p553-f29r-v33g and 3 more.