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

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-10-26 · updated 2026-06-17
Weakness: CWE-89

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.

Affected products

Socket.io-Parser: before 3.3.3; from 3.4.0 before 3.4.2; from 4.0.0 before 4.0.5; from 4.1.0 before 4.2.1 — fixed in 3.3.3, 3.4.2, 4.0.5, 4.2.1

How to fix

Upgrade to a fixed version: Socket.io-Parser 3.3.3, 3.4.2, 4.0.5, 4.2.1. Check the vendor advisory for mitigations.

References

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

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