hono Improperly Handles JSX Attribute Names Allows HTML Injection in hono/jsx SSR

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-56761: 0.29% estimated exploitation activity in the next 30 days; percentile 22.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

16 Apr 2026, 01:02 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-458j-xx4x-4375

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-458j-xx4x-4375

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# Patch Next advisory brief: CVE-2026-56761

Advisory: hono Improperly Handles JSX Attribute Names Allows HTML Injection in hono/jsx SSR
IDs: CVE-2026-56761, GHSA-458j-xx4x-4375
Record: https://patchnext.com/advisories/cve-2026-56761 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.14. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected < 4.12.14; fixed in 4.12.14

## Suggested inspection (read-only)
- `npm ls hono --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on hono.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-458j-xx4x-4375 (OSV record GHSA-458j-xx4x-4375 lists affected ranges: npm hono >=0 <4.12.14 (fixed))
- Verified: https://github.com/advisories/GHSA-458j-xx4x-4375 (GitHub-reviewed advisory GHSA-458j-xx4x-4375 lists affected ranges: npm hono >=0 <4.12.14)

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