GHSA-25hc-qcg6-38wj is a high-severity (CVSS 7.3) Improper Input Validation vulnerability in socket.io. O3 Security confirms whether GHSA-25hc-qcg6-38wj is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
socket.io has an unhandled 'error' event
Real-World Exposure
socket.io📦socket.ioReal-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
Impact
A specially crafted Socket.IO packet can trigger an uncaught exception on the Socket.IO server, thus killing the Node.js process.
node:events:502
throw err; // Unhandled 'error' event
^
Error [ERR_UNHANDLED_ERROR]: Unhandled error. (undefined)
at new NodeError (node:internal/errors:405:5)
at Socket.emit (node:events:500:17)
at /myapp/node_modules/socket.io/lib/socket.js:531:14
at process.processTicksAndRejections (node:internal/process/task_queues:77:11) {
code: 'ERR_UNHANDLED_ERROR',
context: undefined
}
Affected versions
| Version range | Needs minor update? |
|---|---|
4.6.2...latest | Nothing to do |
3.0.0...4.6.1 | Please upgrade to [email protected] (at least) |
2.3.0...2.5.0 | Please upgrade to [email protected] |
Patches
This issue is fixed by https://github.com/socketio/socket.io/commit/15af22fc22bc6030fcead322c106f07640336115, included in [email protected] (released in May 2023).
The fix was backported in the 2.x branch today: https://github.com/socketio/socket.io/commit/d30630ba10562bf987f4d2b42440fc41a828119c
Workarounds
As a workaround for the affected versions of the socket.io package, you can attach a listener for the "error" event:
io.on("connection", (socket) => {
socket.on("error", () => {
// ...
});
});
For more information
If you have any questions or comments about this advisory:
- Open a discussion here
Thanks a lot to Paul Taylor for the responsible disclosure.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | socket.io | all versions | 2.5.1 |
| 📦npm | socket.io | ≥ 3.0.0&&< 4.6.2 | 4.6.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for socket.io. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update socket.io to 2.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-25hc-qcg6-38wj is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether GHSA-25hc-qcg6-38wj is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-25hc-qcg6-38wj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-25hc-qcg6-38wj in your dependencies?
O3 detects GHSA-25hc-qcg6-38wj across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.