CVE-2026-73565 is a medium-severity (CVSS 5.3) CWE-401 vulnerability in @hono/node-server. A fix is available for @hono/node-server — see the affected versions and patch details below.
@hono/node-server: Unauthenticated memory-leak DoS via aborted WebSocket handshake
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-73565 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@hono/node-servernpmDescription
Summary
A WebSocket upgrade request to an upgradeWebSocket route with a missing or malformed Sec-WebSocket-Key header leaks memory permanently. The request's IncomingMessage is retained in an internal map and a pending promise is never settled, even though no connection is established. Since the route is reachable pre-handshake without authentication, an unauthenticated attacker can flood it to gradually exhaust memory.
Details
The built-in WebSocket helper cleans up its internal map only on a successful handshake or when the route guard rejects the request. When ws aborts the handshake because Sec-WebSocket-Key is missing or malformed, no connection event is emitted, so neither cleanup path runs and the entry is retained forever. A present-but-malformed key leaks identically, so a proxy that only checks for the header's presence does not mitigate it.
Impact
An unauthenticated attacker can flood any public upgradeWebSocket route with malformed-key upgrade requests, causing unbounded memory growth and eventual loss of availability. No confidentiality or integrity impact.
Reported by @TarPeg007.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @hono/node-server | ≥ 2.0.0&&< 2.0.10 | 2.0.10npm install @hono/node-server@2.0.10 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @hono/node-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @hono/node-server to 2.0.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73565 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
The vulnerability in `@hono/node-server` is rated Moderate. An unauthenticated attacker can trigger a denial of service by sending malformed WebSocket upgrade requests, leading to unbounded memory growth.
To mitigate this issue, restrict network access to the affected Grafana instance to trusted clients only. This can be achieved by configuring firewall rules to limit incoming connections to the port Grafana listens on. If the service is reloaded or restarted, ensure firewall rules persist.Source: Red Hat security advisory for CVE-2026-73565 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-73565 in your dependencies?
Find it across npm, including transitive dependencies.