Hono: Unbounded dot-notation nesting in parseBody() can cause memory exhaustion

Exploitation

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

CVSS

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

EPSS

• CVE-2026-84364: 0.53% estimated exploitation activity in the next 30 days; percentile 44.81 (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 When parseBody() expands dot-separated form field names into nested objects, it does not limit the nesting depth or the total number of objects created. A request body well within a normal size limit can therefore allocate an object graph far larger than the request itself, and concurrent requests can exhaust the heap and terminate the process. Details Each dot-separated segment of a field name creates an intermediate object. Neither the segments within a single field name nor the total across a request was bounded, and empty segments were preserved, so a field name could encode one nesting level per byte. Both shapes produce the effect: a single deeply dotted field name, and a large number of shallowly dotted ones within one body. A request body size limit does not prevent it, because the amplification happens after the body has been accepted. Dot-notation parsing is not enabled by default. Impact An attacker who can reach an endpoint that parses request bodies with…

Published by the source

8 Sep 2026, 21:23 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-g6gw-c38x-mqfc

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-g6gw-c38x-mqfc

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-g6gw-c38x-mqfc

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-84364

Advisory: Hono: Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion
IDs: CVE-2026-84364, GHSA-g6gw-c38x-mqfc
Record: https://patchnext.com/advisories/cve-2026-84364 (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 5.3)
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-g6gw-c38x-mqfc (GitHub-reviewed advisory GHSA-g6gw-c38x-mqfc lists affected ranges: npm hono >=0 <4.13.5)
- Verified: https://osv.dev/vulnerability/GHSA-g6gw-c38x-mqfc (OSV record GHSA-g6gw-c38x-mqfc lists affected ranges: npm hono >=0 <4.13.5 (fixed))

Commands are suggestions: review each one before running it.