Summary
Hono: memo() retains SSR output across requests, leading to cross-user data disclosure
memo() from hono/jsx retains the result of a server-side render and reuses it for later renders with comparator-equal props. 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.
Details
Components wrapped with memo() are compared by props alone. Values read implicitly during rendering do not participate: JSX Context through createContext() and useContext(), useRequestContext() from hono/jsx-renderer, and getContext() from hono/context-storage. The retained result lives as long as the wrapped component, so it outlives the request that produced it.
Per-request context isolation is not what fails: the current request's values are established correctly, but the memoized component is skipped before anything reads them.
This issue arises when a component wrapped in memo() obtains user- or request-specific data from an ambient context instead of through props.
Impact
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.
This may lead to:
- Disclosure of another user's account or profile data
- Disclosure of request-scoped secrets embedded in HTML, such as CSRF tokens
- Exposure of role-specific content to users who should not receive it
Exploitation depends on the order in which renders populate the retained value and on both requests reaching the same warm instance.
This issue affects applications that render with hono/jsx on the server and wrap a component reading ambient request state in memo(). Applications that pass all request-specific values through props, or that do not use memo(), are unaffected. Client-side rendering is unaffected.
CVE-2026-71850 has a CVSS score of 4.8 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.12.34); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-71850? CVE-2026-71850 is a medium-severity security vulnerability in hono (npm), affecting versions >= 3.8.0, < 4.12.34. It is fixed in 4.12.34.
- How severe is CVE-2026-71850? CVE-2026-71850 has a CVSS score of 4.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of hono are affected by CVE-2026-71850? hono (npm) versions >= 3.8.0, < 4.12.34 is affected.
- Is there a fix for CVE-2026-71850? Yes. CVE-2026-71850 is fixed in 4.12.34. Upgrade to this version or later.
- Is CVE-2026-71850 exploitable, and should I be worried? Whether CVE-2026-71850 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-71850 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-71850? Upgrade
honoto 4.12.34 or later.