CVE-2026-59895
Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility
Description
Hono is a Web application framework that provides support for any JavaScript runtime. From 4.0.0 before 4.12.27, cx() in hono/css composes class names from plain strings but marks the result as already escaped without HTML-escaping the input, allowing untrusted className values used in a JSX class attribute during server-side rendering to break out of the attribute and inject arbitrary markup. This issue is fixed in version 4.12.27.
INFO
Published Date :
July 8, 2026, 5:17 p.m.
Last Modified :
July 10, 2026, 7:53 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Hono to version 4.12.27 or later.
- Validate all className inputs to cx().
- Ensure JSX class attributes are properly escaped.
Public PoC/Exploit Available at Github
CVE-2026-59895 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-59895.
| URL | Resource |
|---|---|
| https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc | Patch |
| https://github.com/honojs/hono/releases/tag/v4.12.27 | Release Notes |
| https://github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-59895 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-59895
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-59895 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-59895 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 10, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:hono:hono:*:*:*:*:*:node.js:*:* versions from (including) 4.0.0 up to (excluding) 4.12.27 Added Reference Type GitHub, Inc.: https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc Types: Patch Added Reference Type GitHub, Inc.: https://github.com/honojs/hono/releases/tag/v4.12.27 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59 Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 08, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-59895', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-08T17:50:18.277447Z'} -
New CVE Received by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'honojs', 'product': 'hono', 'versions': [{'status': 'affected', 'version': '>= 4.0.0, < 4.12.27'}]}] Added Description Hono is a Web application framework that provides support for any JavaScript runtime. From 4.0.0 before 4.12.27, cx() in hono/css composes class names from plain strings but marks the result as already escaped without HTML-escaping the input, allowing untrusted className values used in a JSX class attribute during server-side rendering to break out of the attribute and inject arbitrary markup. This issue is fixed in version 4.12.27. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Added CWE CWE-79 Added CWE CWE-116 Added Reference https://github.com/honojs/hono/commit/cd3f6f7194f0e5c9d4b26ae0cf232018d0f388fc Added Reference https://github.com/honojs/hono/releases/tag/v4.12.27 Added Reference https://github.com/honojs/hono/security/advisories/GHSA-w62v-xxxg-mg59