CVE-2022-2421Public exploitNetwork attack vector

Function-reference injection via unchecked attachment indexes

Published Oct 25, 2022 · Updated Mar 11, 2025

Improper type validation in socket.io-parser allows remote attackers to inject function references through crafted Socket.IO binary packets. In _reconstructPacket, a truthy _placeholder causes data.num to index the buffer array without checking that it is an in-range number, so inherited property names resolve to functions. Affected releases are before 3.3.3, 3.4.0 through 3.4.1, 4.0.0 through 4.0.4, and 4.1.0 through 4.2.0; exposure requires applications not to validate reconstructed values.

CVSS severity10.0
Critical
EPSS probability1.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper type validation in socket.io-parser allows remote attackers to inject function references through crafted Socket.IO binary packets. In _reconstructPacket, a truthy _placeholder causes data.num to index the buffer array without checking that it is an in-range number, so inherited property names resolve to functions. Affected releases are before 3.3.3, 3.4.0 through 3.4.1, 4.0.0 through 4.0.4, and 4.1.0 through 4.2.0; exposure requires applications not to validate reconstructed values.

The record

CVE
CVE-2022-2421
Published
Oct 25, 2022
Updated
Mar 11, 2025
Vendor
Socket.IO
Product
socket.io-parser
Classifications
CWE-1287, CWE-20, CWE-89
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 25, 2022CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.x <4.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Socket.IO · socket.io-parserversion=4.x <4.2.1

Published CVSS scores

9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0Dutch Institute for Vulnerability DisclosureCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1287Improper Validation of Specified Type of Input
CWE-20Improper Input Validation
CWE-89Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo