CVE-2026-44458: Hono Hono Has CSS Declaration Injection Vulnerability

MODERATE
Advisory Identifier: GHSA-qp7p-654g-cw7p
Share
CVSS 4.3
CWE-116 CWE-74
Published
Advisory Summary

CVE-2026-44458 is a MODERATE (CVSS 4.3) hono has css declaration injection vulnerability (CWE-116: Improper Encoding or Escaping of Output) affecting Hono libraries in the npm ecosystem. The issue involves hono has css declaration injection via style object values in jsx ssr. Remediation is available by upgrading affected packages to version 4.12.18.

CVE-2026-44458 at a Glance

CVE Identifier CVE-2026-44458
GHSA Identifier GHSA-qp7p-654g-cw7p
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-116: Improper Encoding or Escaping of Output
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-44458

To remediate this vulnerability, upgrade all affected Hono dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hono fixed: 4.12.18 
npm install hono@4.12.18
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls hono

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-44458, inspect your project dependencies using npm:

npm ls hono

Analyze the terminal output to locate any version of Hono in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.12.18), your application is affected.

Note: The npm ls hono command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-116: Improper Encoding or Escaping of Output, where the product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. as a result, the intended structure of the message is not preserved. In Hono, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary 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. ### Details `style` object values are serialized into a CSS declaration list and escaped for HTML attribute context only. Characters that act as CSS declaration boundaries — such as `;`, comment markers, quoted strings, and block delimiters — are valid in HTML attribute content and can extend a value beyond its assigned property. This issue arises when untrusted input is interpolated into a JSX `style` object and rendered server-side. ### Impact An attacker who can control the value or property name of a `style` object may inject arbitrary CSS declarations. This may lead to: - Visual manipulation of the page, including full-viewport overlays usable for phishing - Outbound requests to attacker-controlled hosts via CSS resource references such as `url(...)` - Hijacking of UI affordances through layout, positioning, or visibility changes This issue affects applications that render JSX on the server with `style` object values or property names derived from untrusted input.

CVE-2026-44458 Affected Hono Versions

1 component(s)
Fixed Versions:
4.12.18
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
< 4.12.18
4.12.18

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-qp7p-654g-cw7p
Hono Source Repository REPOSITORY
https://github.com/honojs/hono

Frequently Asked Questions

What is CVE-2026-44458?
CVE-2026-44458 is a security vulnerability in Hono involving Hono has CSS Declaration Injection via Style Object Values in JSX SSR under CWE-116: Improper Encoding or Escaping of Output.
Which Hono versions are affected?
Affected versions include releases prior to 4.12.18 across affected packages: hono.
What version fixes CVE-2026-44458?
Upgrading to 4.12.18 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.12.18. Upgrade your dependency to 4.12.18 or later.
What is the CVSS score of CVE-2026-44458?
CVE-2026-44458 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-44458?
CVE-2026-44458 is classified under CWE-116: Improper Encoding or Escaping of Output (The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.).
How can I check npm dependencies for CVE-2026-44458?
Run the dependency tree command: 'npm ls hono'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qp7p-654g-cw7p",
  "modified" : "2026-05-09T00:46:44Z",
  "published" : "2026-05-09T00:46:44Z",
  "aliases" : [ "CVE-2026-44458" ],
  "summary" : "Hono has CSS Declaration Injection via Style Object Values in JSX SSR",
  "details" : "### Summary\n\nThe 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.\n\n### Details\n\n`style` object values are serialized into a CSS declaration list and escaped for HTML attribute context only. Characters that act as CSS declaration boundaries — such as `;`, comment markers, quoted strings, and block delimiters — are valid in HTML attribute content and can extend a value beyond its assigned property.\n\nThis issue arises when untrusted input is interpolated into a JSX `style` object and rendered server-side.\n\n### Impact\n\nAn attacker who can control the value or property name of a `style` object may inject arbitrary CSS declarations. This may lead to:\n\n- Visual manipulation of the page, including full-viewport overlays usable for phishing\n- Outbound requests to attacker-controlled hosts via CSS resource references such as `url(...)`\n- Hijacking of UI affordances through layout, positioning, or visibility changes\n\nThis issue affects applications that render JSX on the server with `style` object values or property names derived from untrusted input.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.12.18"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-qp7p-654g-cw7p"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-74" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-09T00:46:44Z",
    "nvd_published_at" : null
  }
}