# CVE-2026-73565: @hono/node-server: Unauthenticated memory-leak DoS via aborted WebSocket handshake

> An unauthenticated attacker can cause a denial of service by sending malformed WebSocket handshake requests that leak memory in the Hono Node.js server library.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** CLEANSTART-2026-EE86998, GHSA-9mqv-5hh9-4cgg

## What is CVE-2026-73565?

CVE-2026-73565 is a medium-severity denial of service vulnerability in honojs node-server, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

@hono/node-server allows running the Hono application on Node.js. From 2.0.0 until 2.0.10, a WebSocket upgrade request to an upgradeWebSocket route with a missing or malformed Sec-WebSocket-Key header causes src/websocket.ts to retain the request's IncomingMessage in waiterMap and leave waitForWebSocket pending because ws.handleUpgrade emits no connection event. The aborted handshake therefore has no cleanup path, allowing an unauthenticated attacker to flood a public route, cause unbounded memory growth, and eventually make the service unavailable. This issue is fixed in version 2.0.10.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-73565?

2 open source packages ship an affected version, including @hono/node-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@hono/node-server` | npm | From 2.0.0 | 2.0.10 |
| `@hono/node-server` | npm | From 2.0.0 | 2.0.10 |

## How do I fix CVE-2026-73565?

Upgrade @hono/node-server to 2.0.10 or later.

## Is CVE-2026-73565 being exploited?

There is no known exploitation of CVE-2026-73565 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73565 and fix it if it is affected.

What it is: CVE-2026-73565 is a medium-severity denial of service vulnerability in honojs node-server, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-73565 in the wild and no public exploit code.

Affected packages and fixed versions:
- @hono/node-server (npm): affected from 2.0.0; fixed in 2.0.10
- @hono/node-server (npm): affected from 2.0.0; fixed in 2.0.10

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-73565/ (Markdown: https://insights.sbomify.com/CVE-2026-73565/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73565
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73565
- OSV: https://osv.dev/vulnerability/CVE-2026-73565

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73565/
Summaries are generated and may contain mistakes; the official description above is the record.