What is CVE-2026-44458?

CVE-2026-44458 is a medium-severity vulnerability in Hono, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 4.3/10. Published 2026-05-13.

How severe is CVE-2026-44458?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Hono

CVE-2026-44458

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.

Published 2026-05-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (24.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 24.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

Hono
Honojs Hono — versions < 4.12.18

Weakness classification (CWE)

References

github.com/honojs/hono/security/advisories/GHSA-qp7p-654g-cw7p (Vendor Advisory)

Frequently asked questions

What is CVE-2026-44458?: CVE-2026-44458 is a medium-severity vulnerability in Hono, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 4.3/10. Published 2026-05-13.
How severe is CVE-2026-44458?: Medium severity. CVSS v3 base score is 4.3 out of 10.