Is CVE-2026-59895 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-59895 being exploited in the wild.

How severe is CVE-2026-59895?

Medium severity, with a CVSS score of 6.1, published 8 July 2026.

Which products and versions are affected?

hono (npm) >= 4.0.0, < 4.12.27, SEMVER:introduced=4.0.0,fixed=4.12.27.

Is there a fix for CVE-2026-59895?

Yes. hono (npm): upgrade to 4.12.27 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-59895 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-59895?

Check whether you run hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-59895: Hono XSS in hono/css cx() utility

Q: Which products and versions are affected?

hono (npm) >= 4.0.0, < 4.12.27, SEMVER:introduced=4.0.0,fixed=4.12.27.

Q: Is there a fix for CVE-2026-59895?

Yes. hono (npm): upgrade to 4.12.27 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-59895 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-59895?

Check whether you run hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-59895 · Severity: medium · CVSS 6.1 · Published 2026-07-08

A vulnerability in the Hono web framework could allow attackers to inject malicious scripts into web pages. Hono is a popular tool used by developers to build fast web applications. If an application uses a specific styling utility with data provided by a user, an attacker could take over user sessions or steal sensitive information like login credentials.

Technologies: hono (npm). Vendors: npm.

Quick answers

Is CVE-2026-59895 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-59895 being exploited in the wild.
How severe is CVE-2026-59895?: Medium severity, with a CVSS score of 6.1, published 8 July 2026.
Which products and versions are affected?: hono (npm) >= 4.0.0, < 4.12.27, SEMVER:introduced=4.0.0,fixed=4.12.27.
Is there a fix for CVE-2026-59895?: Yes. hono (npm): upgrade to 4.12.27 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59895 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-59895?: Check whether you run hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

hono (npm): upgrade to 4.12.27 or later
```
npm install hono@4.12.27
```

Technical details

A Cross-Site Scripting (XSS) vulnerability exists in Hono's `cx()` utility within the `hono/css` package. The `cx()` function composes CSS class names but incorrectly marks the resulting string as 'already escaped' without actually performing HTML entity encoding on the input. When this result is used in a JSX `class` attribute during server-side rendering (SSR), an attacker can provide input containing quotes to break out of the attribute and inject arbitrary HTML or JavaScript. This requires the application to pass untrusted, user-controlled strings to `cx()`. The issue is resolved in version 4.12.27.

Affected products

honojs hono >= 4.0.0, < 4.12.27

Identifiers

CVE-2026-59895
GHSA-w62v-xxxg-mg59

Timeline

2026-06-23: patched: Fixed in version 4.12.27
2026-07-21: advisory: GitHub Advisory published

References

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