CVE-2026-59896
ADVISORY - githubSummary
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
Common Weakness Enumeration (CWE)
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
GitHub
2.2
CVSS SCORE
6.5medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| hono | npm | - | - | >=4.11.8,<4.12.27 | 4.12.27 |
CVSS:3 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
A successful attack depends on conditions beyond the attacker's control, requiring investing a measurable amount of effort in research, preparation, or execution against the vulnerable component before a successful attack.
The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any user.
An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
There is no impact to availability within the impacted component.