CVE-2026-44458 Hono: CSS Declaration Injection via Style Object Values in JSX SSR
Attackers can inject CSS declarations via style objects in Hono JSX SSR, potentially altering page appearance or enabling UI redressing attacks.
- 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-2026-44458?
CVE-2026-44458 is a medium-severity cross-site scripting vulnerability in honojs hono, published on 13 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 4.12.18, the JSX renderer escapes style attribute object values for HTML but not for CSS. Untrusted input in a style object value or property name can therefore inject additional CSS declarations into the rendered style attribute. The impact is limited to CSS and does not allow JavaScript execution or HTML attribute breakout. This vulnerability is fixed in 4.12.18.
Which versions are affected by CVE-2026-44458?
2 open source packages ship an affected version, including hono. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | All versions | 4.12.18 |
hono npm | All versions | 4.12.18 |
Products include Hono Hono.
How do I fix CVE-2026-44458?
Upgrade hono to 4.12.18 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-44458 being exploited?
There is no known exploitation of CVE-2026-44458 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 CLEANSTART-2026-EO52951, CLEANSTART-2026-EQ24624, ECHO-63bb-4218-a72e, GHSA-qp7p-654g-cw7p, MINI-5jrh-xjj6-q9mr, MINI-68wm-fm8q-f8wg and 8 more.