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

> A specially crafted HTTP request triggers an uncaught exception in Engine.IO, crashing the Node.js process and causing denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2023
- **Updated:** 13 Feb 2025
- **Also known as:** GHSA-q9mw-68c2-j6m5

## What is CVE-2023-31125?

CVE-2023-31125 is a medium-severity denial of service vulnerability in socketio engine.io, published on 8 May 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2023-31125?

2 open source packages ship an affected version, including engine.io. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `engine.io` | npm | From 5.1.0 | 6.4.2 |
| `engine.io` | npm | From 5.1.0 | 6.4.2 |

Products: Socket Engine.io.

## How do I fix CVE-2023-31125?

Upgrade engine.io to 6.4.2 or later.

## Is CVE-2023-31125 being exploited?

There is no known exploitation of CVE-2023-31125 in the wild and no public exploit code.

## Other vulnerabilities in socketio engine.io

- [CVE-2026-59724](https://insights.sbomify.com/CVE-2026-59724/): Socket.IO: Engine.IO WebTransport SID DoS (high 7.5)
- [CVE-2026-59725](https://insights.sbomify.com/CVE-2026-59725/): Socket.IO: Engine.IO Polling Transport Connection Exhaustion (high 7.5)
- [CVE-2022-21676](https://insights.sbomify.com/CVE-2022-21676/): Uncaught Exception in engine.io (high 7.5)
- [CVE-2020-36048](https://insights.sbomify.com/CVE-2020-36048/): Resource exhaustion in engine.io (high 7.5)
- [CVE-2022-41940](https://insights.sbomify.com/CVE-2022-41940/): Uncaught exception in engine.io (high 7.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-31125 and fix it if it is affected.

What it is: CVE-2023-31125 is a medium-severity denial of service vulnerability in socketio engine.io, published on 8 May 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-31125 in the wild and no public exploit code.

Affected packages and fixed versions:
- engine.io (npm): affected from 5.1.0; fixed in 6.4.2
- engine.io (npm): affected from 5.1.0; fixed in 6.4.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-31125/ (Markdown: https://insights.sbomify.com/CVE-2023-31125/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-31125
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-31125
- OSV: https://osv.dev/vulnerability/CVE-2023-31125

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-31125/
Summaries are generated and may contain mistakes; the official description above is the record.