CVE-2022-21676 is a high-severity (CVSS 7.5) CWE-754 vulnerability in engine.io. A fix is available for engine.io — see the affected versions and patch details below.
Uncaught Exception in engine.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-2022-21676.
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-2022-21676 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 377,166 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.
engine.ionpmDescription
Engine.IO is the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, thus killing the Node.js process. This impacts all the users of the engine.io package starting from version 4.0.0, including those who uses depending packages like socket.io. Versions prior to 4.0.0 are not impacted. A fix has been released for each major branch, namely 4.1.2 for the 4.x.x branch, 5.2.1 for the 5.x.x branch, and 6.1.1 for the 6.x.x branch. There is no known workaround except upgrading to a safe version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | engine.io | ≥ 4.0.0&&< 4.1.2 | 4.1.2npm install engine.io@4.1.2 |
| 📦npm | engine.io | ≥ 5.0.0&&< 5.2.1 | 5.2.1npm install engine.io@5.2.1 |
| 📦npm | engine.io | ≥ 6.0.0&&< 6.1.1 | 6.1.1npm install engine.io@6.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for engine.io, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update engine.io to 4.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-21676 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-2022-21676 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-21676. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-21676 in your dependencies?
O3 Security finds CVE-2022-21676 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.