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CVE-2021-30661 — A use after free issue was addressed with improved memory management.

Key facts

CVE-2021-30661 is a High (8.8) vulnerability: A use after free issue was addressed with improved memory management.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2021-11-03), confirming active exploitation in the wild.

Actively exploited — on the CISA KEV catalog

CVE-2021-30661 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2021-11-03), confirming exploitation in the wild. Federal remediation deadline: 2021-11-17. Prioritise patching and deploy the detection and prevention rules below.
CVE CVE-2021-30661
Severity High (8.8)
CISA KEV Actively exploited (added 2021-11-03)
Detection / prevention —
PoC poc.py
Source 2021/CVE-2021-30661/

Details

English | 한국어

Description

A use after free issue was addressed with improved memory management. This issue is fixed in Safari 14.1, iOS 12.5.3, iOS 14.5 and iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Vulnerability Details

Property Value
CVE ID CVE-2021-30661
CVSS Score 8.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2021/CVE-2021-30661/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-2021-30661

# 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://support.apple.com/en-us/HT212317
  • https://support.apple.com/en-us/HT212318
  • https://support.apple.com/en-us/HT212323
  • https://support.apple.com/en-us/HT212324
  • https://support.apple.com/en-us/HT212325
  • https://support.apple.com/en-us/HT212341
  • https://support.apple.com/en-us/HT212317
  • https://support.apple.com/en-us/HT212318
  • https://support.apple.com/en-us/HT212323
  • https://support.apple.com/en-us/HT212324
  • https://support.apple.com/en-us/HT212325
  • https://support.apple.com/en-us/HT212341
  • https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30661

Generated by PoC Generator on 2026-07-09T20:11:00.602589749

Frequently asked questions

What is CVE-2021-30661?

CVE-2021-30661 is a High (8.8) vulnerability: A use after free issue was addressed with improved memory management.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2021-11-03), confirming active exploitation in the wild.

How do I detect CVE-2021-30661?

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-2021-30661?

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-2021-30661 actively exploited?

Yes. CVE-2021-30661 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2021-11-03, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2021-11-17. Prioritise patching and deploy the detection and prevention rules above.

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