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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.8 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-71850: 0.27% estimated exploitation activity in the next 30 days; percentile 18.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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…

Published by the source

7 Aug 2026, 18:42 UTC

Last modified by the source

7 Aug 2026, 18:42 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-f23p-vx2j-j53r

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# Patch Next advisory brief: CVE-2026-71850

Advisory: Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure
IDs: CVE-2026-71850, GHSA-f23p-vx2j-j53r
Record: https://patchnext.com/advisories/cve-2026-71850 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.12.34. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected >= 3.8.0, < 4.12.34; fixed in 4.12.34

## Suggested inspection (read-only)
- `npm ls hono --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on hono.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-f23p-vx2j-j53r (GitHub-reviewed advisory GHSA-f23p-vx2j-j53r lists affected ranges: npm hono >=3.8.0 <4.12.34)

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