CVE-2026-44455 — hono
MEDIUMCVE-2026-44455 is a medium-severity (CVSS 4.7) CWE-74 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.
Hono: Unvalidated JSX Tag Names in hono/jsx May Allow HTML Injection
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44455.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
hononpmDescription
Summary
Improper handling of JSX element tag names in hono/jsx allowed unvalidated tag names to be directly inserted into the generated HTML output.
When untrusted input is used as a tag name via the programmatic jsx() or createElement() APIs during server-side rendering, specially crafted values may break out of the intended element context and inject unintended HTML.
Details
When rendering JSX elements to HTML strings, attribute values are escaped and attribute names are validated. However, element tag names were previously inserted into the output without validation.
If a tag name contains characters such as <, >, quotes, or whitespace, it may alter the structure of the generated HTML.
For example, malformed tag names can:
- Break out of the intended element and introduce unintended HTML elements
- Inject attributes or event handlers into the rendered output
This issue arises when untrusted input (such as query parameters or database content) is used as JSX tag names via jsx() or createElement() during server-side rendering.
Impact
An attacker who can control tag names used in JSX rendering may inject unintended HTML into the generated output.
This may lead to:
- Injection of unexpected HTML elements or attributes
- Corruption of the HTML structure
- Cross-site scripting (XSS) when combined with unsafe usage patterns
This issue only affects applications that construct JSX tag names from untrusted input. Applications using static or allowlisted tag names are not affected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | all versions | 4.12.16npm install hono@4.12.16 |
Affected Products
honohonoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hono to 4.12.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44455 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-44455 in your dependencies?
Find it across npm, including transitive dependencies.