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MEDIUM severity

CVE-2026-126343 — @hono/node-server

MEDIUMFix: honojs/node-server@61cc026

CVE-2026-126343 is a medium-severity (CVSS 5.3) CWE-248 vulnerability in @hono/node-server. A fix is available for @hono/node-server — see the affected versions and patch details below.

@hono/node-server: Unhandled `ECONNRESET` on the socket during an asynchronous WebSocket upgrade crashes the process

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected
📦@hono/node-server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

Summary

While @hono/node-server waits for the Hono application to handle a WebSocket upgrade request, the socket has no error listener. If the client resets the TCP connection during that time, the resulting ECONNRESET is emitted as an unhandled 'error' event and the process terminates.

Details

The upgrade handler awaits the application before attaching any listener to the socket. When middleware on the upgrade path does asynchronous work, such as an authentication lookup, a connection reset in that window has no handler. If a global uncaughtException handler swallows the error, the pending upgrade is never released and its entry is retained for the lifetime of the process.

The fix attaches error and close listeners to the socket before calling the application, releases the pending upgrade when the socket closes, and skips the handshake on a destroyed socket.

Impact

An unauthenticated client can terminate the server process with a single connection by sending a WebSocket upgrade request and resetting the connection before the application has responded. Where the crash is suppressed, repeated requests grow the heap.

This affects applications that enable WebSocket support in @hono/node-server and run asynchronous middleware or handlers on the upgrade path.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npm@hono/node-server≥ 2.0.0&&< 2.1.62.1.6npm install @hono/node-server@2.1.6

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. Fix

    Update @hono/node-server to 2.1.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126343 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary While `@hono/node-server` waits for the Hono application to handle a WebSocket upgrade request, the socket has no error listener. If the client resets the TCP connection during that time, the resulting `ECONNRESET` is emitted as an unhandled `'error'` event and the process terminates. ### Details The upgrade handler awaits the application before attaching any listener to the socket. When middleware on the upgrade path does asynchronous work, such as an authentication lookup, a connection reset in that window has no handler. If a global `uncaughtException` handler swallows the er
O3 Security · Impact-Aware SCA

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