GHSA-q9mw-68c2-j6m5 is a medium-severity (CVSS 6.5) CWE-248 vulnerability in engine.io. O3 Security confirms whether GHSA-q9mw-68c2-j6m5 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
engine.io Uncaught Exception vulnerability
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
engine.ionpmDescription
Impact
A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, thus killing the Node.js process.
TypeError: Cannot read properties of undefined (reading 'handlesUpgrades')
at Server.onWebSocket (build/server.js:515:67)
This impacts all the users of the engine.io package, including those who uses depending packages like socket.io.
Patches
A fix has been released today (2023/05/02): 6.4.2
This bug was introduced in version 5.1.0 and included in version 4.1.0 of the socket.io parent package. Older versions are not impacted.
For socket.io users:
| Version range | engine.io version | Needs minor update? |
|---|---|---|
[email protected] | ~6.4.0 | npm audit fix should be sufficient |
[email protected] | ~6.2.0 | Please upgrade to [email protected] |
[email protected] | ~6.1.0 | Please upgrade to [email protected] |
[email protected] | ~6.0.0 | Please upgrade to [email protected] |
[email protected] | ~5.2.0 | Please upgrade to [email protected] |
[email protected] | ~5.1.1 | Please upgrade to [email protected] |
[email protected] | ~5.0.0 | Not impacted |
[email protected] | ~4.1.0 | Not impacted |
[email protected] | ~4.0.0 | Not impacted |
[email protected] | ~3.6.0 | Not impacted |
[email protected] and below | ~3.5.0 | Not impacted |
Workarounds
There is no known workaround except upgrading to a safe version.
For more information
If you have any questions or comments about this advisory:
- Open an issue in
engine.io
Thanks to Thomas Rinsma from Codean for the responsible disclosure.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | engine.io | ≥ 5.1.0&&< 6.4.2 | 6.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for engine.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 engine.io to 6.4.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-q9mw-68c2-j6m5 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-q9mw-68c2-j6m5 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-q9mw-68c2-j6m5. 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-q9mw-68c2-j6m5 in your dependencies?
O3 detects GHSA-q9mw-68c2-j6m5 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.