Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials

Exploitation

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

CVSS

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

EPSS

• CVE-2026-84363: 0.45% estimated exploitation activity in the next 30 days; percentile 39.02 (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 Hono's query parsing does not stop at the URL fragment: a ? appearing after a

is treated as the start of a query string. As a result, the application can read request parameters that no other component involved in handling the request can see. Details A fragment is never part of the query, and every standard URL consumer — browsers, new URL(), reverse proxies — ignores everything from the first

onward. Hono's routing followed that rule; its query helpers did not. For one and the same request, this produces an interpretation differential: - A component in front of the application that inspects the query string — filtering rules, parameter allow/deny lists, access logging — observes no parameters, while the application reads and acts on them. - The cache middleware removed the fragment when building its cache key, so a response influenced by parameters carried inside the fragment could be stored under a key that did not reflect them and later returned to other users. The…

Published by the source

8 Sep 2026, 21:22 UTC

Last modified by the source

8 Sep 2026, 21:30 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-crvj-82cr-hjcx

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-crvj-82cr-hjcx

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-crvj-82cr-hjcx

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# Patch Next advisory brief: CVE-2026-84363

Advisory: Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials
IDs: CVE-2026-84363, GHSA-crvj-82cr-hjcx
Record: https://patchnext.com/advisories/cve-2026-84363 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hono 4.13.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hono: affected < 4.13.5; fixed in 4.13.5

## 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-crvj-82cr-hjcx (GitHub-reviewed advisory GHSA-crvj-82cr-hjcx lists affected ranges: npm hono >=0 <4.13.5)
- Verified: https://osv.dev/vulnerability/GHSA-crvj-82cr-hjcx (OSV record GHSA-crvj-82cr-hjcx lists affected ranges: npm hono >=0 <4.13.5 (fixed))

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