CVE-2021-1789 — A type confusion issue was addressed with improved state handling.¶

Key facts

CVE-2021-1789 is a High (8.8) vulnerability: A type confusion issue was addressed with improved state handling.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-05-04), confirming active exploitation in the wild.

Actively exploited — on the CISA KEV catalog

CVE-2021-1789 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-05-04), confirming exploitation in the wild. Federal remediation deadline: 2022-05-25. Prioritise patching and deploy the detection and prevention rules below.


CVE	CVE-2021-1789
Severity	High (8.8)
CISA KEV	Actively exploited (added 2022-05-04)
Detection / prevention	—
PoC	poc.py
Source	2021/CVE-2021-1789/

Details¶

English | 한국어

Description¶

A type confusion issue was addressed with improved state handling. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, tvOS 14.4, watchOS 7.3, iOS 14.4 and iPadOS 14.4, Safari 14.0.3. Processing maliciously crafted web content may lead to arbitrary code execution.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2021-1789
CVSS Score	8.8

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2021/CVE-2021-1789/poc.py

Usage¶

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab¶

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start¶

# Clone and navigate to CVE directory
cd CVE-2021-1789

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints¶

Application	URL	Status
Vulnerable App	http://localhost:8080	Shows vulnerability
Patched App	http://localhost:8081	Demonstrates fix

Directory Structure¶

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References¶

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/
https://security.gentoo.org/glsa/202104-03
https://support.apple.com/en-us/HT212146
https://support.apple.com/en-us/HT212147
https://support.apple.com/en-us/HT212148
https://support.apple.com/en-us/HT212149
https://support.apple.com/en-us/HT212152
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/
https://security.gentoo.org/glsa/202104-03
https://support.apple.com/en-us/HT212146
https://support.apple.com/en-us/HT212147
https://support.apple.com/en-us/HT212148
https://support.apple.com/en-us/HT212149
https://support.apple.com/en-us/HT212152
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1789

Generated by PoC Generator on 2026-07-10T00:58:16.403006081

Frequently asked questions¶

What is CVE-2021-1789?¶

CVE-2021-1789 is a High (8.8) vulnerability: A type confusion issue was addressed with improved state handling.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2022-05-04), confirming active exploitation in the wild.

How do I detect CVE-2021-1789?¶

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2021-1789?¶

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

Is CVE-2021-1789 actively exploited?¶

Yes. CVE-2021-1789 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2022-05-04, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2022-05-25. Prioritise patching and deploy the detection and prevention rules above.

For authorized security testing and research only. See the full source and NVD record.