CVE-2026-47675 Hono: Cookie helper does not sanitize sameSite and priority, allowing Set-Cookie injection
Attackers can inject arbitrary attributes into Set-Cookie headers via unsanitized sameSite and priority options in the Hono framework.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-47675?
CVE-2026-47675 is a medium-severity vulnerability in honojs hono, published on 28 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, the serialize() function in hono/cookie validates domain and path options against characters that corrupt Set-Cookie header syntax (;, \r, \n), but does not apply the same validation to sameSite and priority. An application that passes user-controlled input into either option may produce a Set-Cookie response header containing attacker-chosen additional attributes. This vulnerability is fixed in 4.12.21.
Which versions are affected by CVE-2026-47675?
2 open source packages ship an affected version, including hono. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | All versions | 4.12.21 |
hono npm | All versions | 4.12.21 |
Products include Hono Hono.
How do I fix CVE-2026-47675?
Upgrade hono to 4.12.21 or later.
Is CVE-2026-47675 being exploited?
There is no known exploitation of CVE-2026-47675 in the wild and no public exploit code.
Other vulnerabilities in honojs hono
- CVE-2026-27700 Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo
- CVE-2026-22817 JWT Algorithm Confusion via Unsafe Default (HS256) in Hono JWT Middleware Allows Token Forgery and Auth Bypass
- CVE-2026-22818 JWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback)
- CVE-2025-62610 Hono Improperly Authorizes JWT Audience Validation
- CVE-2026-29045 Hono: Arbitrary file access via serveStatic vulnerability
Sources
Also known as ECHO-d26c-09d1-ea7b, GHSA-3hrh-pfw6-9m5x, MINI-39pr-rf8h-4p88, MINI-8j4f-66v7-mqxc, MINI-9fvr-cr74-rh67, MINI-c524-9r7g-x6g6 and 8 more.