How severe is CVE-2026-56761?

No CVSS score has been assigned to CVE-2026-56761 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-56761?

CVE-2026-56761 affects the following packages: hono (npm). Ecosystems affected: npm.

How do I fix CVE-2026-56761?

Update hono to 4.12.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56761 is resolved across your whole dependency graph.

How do I detect CVE-2026-56761 in my npm dependencies?

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.

How do I mitigate CVE-2026-56761 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-56761?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-56761 can be triaged on real exposure rather than presence alone.

Is CVE-2026-56761 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-56761 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-56761?

CVE-2026-56761 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 19th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-56761?

CVE-2026-56761 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-56761 published, and has it been updated?

CVE-2026-56761 was published on June 24, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-56761 — hono

CVE-2026-56761 is a Cross-site Scripting (XSS) vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.

hono - HTML Injection via Improper JSX Attribute Name Handling in SSR

Also known asGHSA-458j-xx4x-4375

Published

Jun 24, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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-2026-56761.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs19th percentile — riskier than 19% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

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.

6Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

hononpm

46.1Mdownloads / week

Description

Summary

Improper handling of JSX attribute names in hono/jsx allows malformed attribute keys to corrupt the generated HTML output.

When untrusted input is used as attribute keys during server-side rendering, specially crafted keys can break out of attribute or tag boundaries and inject unintended HTML.

Details

When rendering JSX elements to HTML strings, attribute values are escaped, but attribute names (keys) were previously inserted into the output without validation.

If an attribute name contains characters such as ", >, or whitespace, it can alter the structure of the generated HTML.

For example, malformed attribute names can:

Break out of the current attribute and introduce unintended additional attributes
Break out of the current HTML tag and inject new elements into the output

This issue arises when untrusted input (such as query parameters or form data) is used as JSX attribute keys during server-side rendering.

Impact

An attacker who can control attribute keys used in JSX rendering may inject unintended attributes or HTML elements into the generated output.

This may lead to:

Injection of unexpected HTML attributes
Corruption of the HTML structure
Potential cross-site scripting (XSS) if combined with unsafe usage patterns

This issue affects applications that pass untrusted input as JSX attribute keys during server-side rendering.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`hono`	all versions	4.12.14`npm install hono@4.12.14`

Detection & mitigation playbook

Open-source dependency

Detect
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 4.12.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56761 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-56761 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-56761. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary Improper handling of JSX attribute names in hono/jsx allows malformed attribute keys to corrupt the generated HTML output. When untrusted input is used as attribute keys during server-side rendering, specially crafted keys can break out of attribute or tag boundaries and inject unintended HTML. ## Details When rendering JSX elements to HTML strings, attribute values are escaped, but attribute names (keys) were previously inserted into the output without validation. If an attribute name contains characters such as `"`, `>`, or whitespace, it can alter the structure of the genera

O3 Security · Impact-Aware SCA

Is CVE-2026-56761 in your dependencies?

O3 Security finds CVE-2026-56761 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works