CVE-2026-59896 is a medium-severity (CVSS 6.5) CWE-362 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.
hono/jsx does not isolate context per request, leading to cross-request data disclosure
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-2026-59896.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-59896 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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.
hononpmDescription
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
jsxRenderermiddleware anduseRequestContext()
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hono | ≥ 4.11.8&&< 4.12.27 | 4.12.27npm install hono@4.12.27 |
Affected Products
honohonoDetection & mitigation playbook
Open-source dependencyDetect
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 4.12.27 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59896 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.
Frequently Asked Questions
Is CVE-2026-59896 in your dependencies?
Find it across npm, including transitive dependencies.