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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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.
Which versions are affected by CVE-2026-73565?
2 open source packages ship an affected version, including @hono/node-server.
| Package | 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-73565 being exploited?
There is no known exploitation of CVE-2026-73565 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-EE86998, GHSA-9mqv-5hh9-4cgg.