Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure

Summary

Hono is a Web application framework that provides support for any JavaScript runtime. From 3.8.0 to 4.12.33, memo() from hono/jsx retains the result of a server side render and reuses it for later renders with comparator equal props, and request scoped values read inside the component take no part in that comparison, so a response can contain HTML rendered for another user's request. Components wrapped with memo() are compared by props alone; values read implicitly during rendering, such as JSX Context through createContext() and useContext(), useRequestContext() from hono/jsx-renderer, and getContext() from hono/context-storage, do not participate, and the retained result lives as long as the wrapped component, so it outlives the request that produced it. A user may receive a response containing HTML rendered for another user when both render the same memoized component with comparator equal props on the same warm instance, which may disclose another user's account or profile data, disclose request scoped secrets embedded in HTML such as CSRF tokens, or expose role specific content to users who should not receive it. This issue is fixed in version 4.12.34.

Timeline

1. Aug 7, 2026, 6:41 PM UTCCVE published
2. Aug 10, 2026, 1:26 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Aug 10, 2026, 1:26 PM UTCRecord last updated

Affected versions

• honojs hono

  From 3.8.0 · fixed in 4.12.34

• hononpm

  From 3.8.0 · fixed in 4.12.34

References 1