CVE-2024-38355 is a high-severity (CVSS 7.3) vulnerability in socket.io. A fix is available for socket.io — see the affected versions and patch details below.
Unhandled 'error' event in socket.io
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-38355.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-38355 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
socket.ionpmDescription
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 | 2.5.1npm install socket.io@2.5.1 |
| 📦npm | socket.io | ≥ 3.0.0&&< 4.6.2 | 4.6.2npm install socket.io@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update socket.io to 2.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-38355 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-38355 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-38355. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
This flaw occurs because the server fails to handle certain errors properly, leading to a complete server shutdown. Since the attack requires no special privileges or user interaction and can be done remotely, it poses a significant risk to server stability and availability. This vulnerability is rated as IMPORTANT…
It is recommended to update to the latest version to address this vulnerability.Source: Red Hat security advisory for CVE-2024-38355 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2024-38355 in your dependencies?
O3 Security finds CVE-2024-38355 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.