CVE-2026-59896: Hono Hono/jsx Does Not Isolate Context Vulnerability

MODERATE
Advisory Identifier: GHSA-hvrm-45r6-mjfj
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CVSS 6.5
CWE-362
Published
Advisory Summary

CVE-2026-59896 is a MODERATE (CVSS 6.5) hono/jsx does not isolate context vulnerability (CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')) affecting Hono libraries in the npm ecosystem. The issue involves hono/jsx does not isolate context per request, leading to cross-request data disclosure. Remediation is available by upgrading affected packages to version 4.12.27.

CVE-2026-59896 at a Glance

CVE Identifier CVE-2026-59896
GHSA Identifier GHSA-hvrm-45r6-mjfj
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.5

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

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

How to Fix CVE-2026-59896

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: 4.12.27 
npm install hono@4.12.27
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-2026-59896, 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 4.12.27), 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-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'), where the product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. 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 `hono/jsx` did not isolate context values per request during server-side rendering. While an async component was suspended on `await`, its provided context value stayed observable to other requests rendering concurrently, so `useContext()` could return a value from a different in-flight request. ### Details During server-side rendering, context values were kept in a process-wide structure rather than scoped to each request's render. While an async component awaited, another request entering the same provider could observe or replace the value; when the first render resumed, it could read the other request's context. This affects the usual ways request-scoped data is passed through a server-rendered JSX tree: - `createContext()` / `useContext()` - the `jsxRenderer` middleware and `useRequestContext()` It arises only when context is read after an `await` inside an async component while requests render concurrently. Reading context synchronously (before any `await`), purely synchronous rendering, and client-side (DOM) rendering are not affected. ### Impact Under concurrent requests, a response could be rendered with another request's context. A user may receive HTML rendered for a different user, and an authorization check performed after an `await` may be evaluated against another user's data. This may lead to: - disclosure of rendered output intended for another user - authorization decisions made with the wrong request's context - cross-request mixing of session or other request-scoped state

CVE-2026-59896 Affected Hono Versions

1 component(s)
Fixed Versions:
4.12.27
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
≥ 4.11.8
< 4.12.27
4.12.27

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-hvrm-45r6-mjfj
NVD — CVE-2026-59896 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59896
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/fab3b13639339cbd5ba1166a5b23d9ac30c5f64f
Hono Source Repository REPOSITORY
https://github.com/honojs/hono
Hono Release RELEASE
https://github.com/honojs/hono/releases/tag/v4.12.27

Frequently Asked Questions

What is CVE-2026-59896?
CVE-2026-59896 is a security vulnerability in Hono involving hono/jsx does not isolate context per request, leading to cross-request data disclosure under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition').
Which Hono versions are affected?
Affected versions include releases prior to 4.12.27 across affected packages: hono.
What version fixes CVE-2026-59896?
Upgrading to 4.12.27 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.12.27. Upgrade your dependency to 4.12.27 or later.
What is the CVSS score of CVE-2026-59896?
CVE-2026-59896 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N.
What CWE is associated with CVE-2026-59896?
CVE-2026-59896 is classified under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.).
How can I check npm dependencies for CVE-2026-59896?
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-hvrm-45r6-mjfj",
  "modified" : "2026-07-21T18:34:19Z",
  "published" : "2026-07-21T18:34:19Z",
  "aliases" : [ "CVE-2026-59896" ],
  "summary" : "hono/jsx does not isolate context per request, leading to cross-request data disclosure",
  "details" : "### Summary\n\n`hono/jsx` did not isolate context values per request during server-side rendering. While an async component was suspended on `await`, its provided context value stayed observable to other requests rendering concurrently, so `useContext()` could return a value from a different in-flight request.\n\n### Details\n\nDuring server-side rendering, context values were kept in a process-wide structure rather than scoped to each request's render. While an async component awaited, another request entering the same provider could observe or replace the value; when the first render resumed, it could read the other request's context.\n\nThis affects the usual ways request-scoped data is passed through a server-rendered JSX tree:\n\n- `createContext()` / `useContext()`\n- the `jsxRenderer` middleware and `useRequestContext()`\n\nIt arises only when context is read after an `await` inside an async component while requests render concurrently. Reading context synchronously (before any `await`), purely synchronous rendering, and client-side (DOM) rendering are not affected.\n\n### Impact\n\nUnder concurrent requests, a response could be rendered with another request's context. A user may receive HTML rendered for a different user, and an authorization check performed after an `await` may be evaluated against another user's data.\n\nThis may lead to:\n\n- disclosure of rendered output intended for another user\n- authorization decisions made with the wrong request's context\n- cross-request mixing of session or other request-scoped state",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N"
  } ],
  "affected" : [ {
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      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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  "references" : [ {
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  }, {
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    "url" : "https://github.com/honojs/hono/commit/fab3b13639339cbd5ba1166a5b23d9ac30c5f64f"
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  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.12.27"
  } ],
  "database_specific" : {
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    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T18:34:19Z",
    "nvd_published_at" : "2026-07-08T17:17:27Z"
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}