CVE-2020-9936 – CVE-2020-9936 is an out-of-bounds write vulnera... (How to Fix)

Q: What is the severity of CVE-2020-9936?

CVE-2020-9936 has a CVSS score of 7.8 (HIGH). CVE-2020-9936 is an out-of-bounds write vulnerability in Apple's image processing components, allowing arbitrary code execution when a malicious image is processed. It affects users of iOS, iPadOS, macOS, tvOS, watchOS, iTunes for Windows, and iCloud for Windows. Exploitation could lead to full system compromise on vulnerable devices.

📋 TL;DR

CVE-2020-9936 is an out-of-bounds write vulnerability in Apple's image processing components, allowing arbitrary code execution when a malicious image is processed. It affects users of iOS, iPadOS, macOS, tvOS, watchOS, iTunes for Windows, and iCloud for Windows. Exploitation could lead to full system compromise on vulnerable devices.

💻 Affected Systems

Products:

iOS
iPadOS
macOS
tvOS
watchOS
iTunes for Windows
iCloud for Windows

Versions: Versions prior to iOS 13.6, iPadOS 13.6, macOS Catalina 10.15.6, tvOS 13.4.8, watchOS 6.2.8, iTunes 12.10.8 for Windows, iCloud for Windows 11.3, iCloud for Windows 7.20.

Operating Systems: iOS, iPadOS, macOS, tvOS, watchOS, Windows

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations of affected software are vulnerable; exploitation requires processing a maliciously crafted image.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full system compromise with arbitrary code execution, potentially leading to data theft, ransomware deployment, or persistent backdoor installation.

🟠

Likely Case

Local privilege escalation or remote code execution via malicious images in apps or web content, resulting in unauthorized access or malware infection.

🟢

If Mitigated

Limited impact if systems are patched or isolated, with potential denial-of-service or minor data corruption if exploitation is partially blocked.

🌐 Internet-Facing: MEDIUM, as exploitation typically requires user interaction (e.g., opening a malicious image), but could be triggered via web or email.

🏢 Internal Only: MEDIUM, as internal users might process malicious images from untrusted sources, but network segmentation can reduce spread.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation is unauthenticated but requires user interaction to process a malicious image; no public proof-of-concept is known, reducing immediate risk.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: iOS 13.6, iPadOS 13.6, macOS Catalina 10.15.6, tvOS 13.4.8, watchOS 6.2.8, iTunes 12.10.8 for Windows, iCloud for Windows 11.3, iCloud for Windows 7.20.

Vendor Advisory: https://support.apple.com/HT211288

Restart Required: Yes

Instructions:

1. Go to Settings > General > Software Update on iOS/iPadOS/watchOS/tvOS, or System Preferences > Software Update on macOS, or check for updates in iTunes/iCloud for Windows. 2. Download and install the latest update. 3. Restart the device or application as prompted.

🔧 Temporary Workarounds

Restrict image sources

all

Avoid opening images from untrusted sources such as unknown emails, websites, or apps to reduce exploitation risk.

Disable automatic image processing

all

Configure email clients and web browsers to disable automatic image loading or processing from external sources.

🧯 If You Can't Patch

Isolate affected systems from untrusted networks and limit user privileges to reduce impact if exploited.
Implement application whitelisting to block unauthorized image processing applications or scripts.

🔍 How to Verify

Check if Vulnerable:

Check the software version against affected versions listed in the Apple advisories; if prior to patched versions, the system is vulnerable.

Check Version:

On Apple devices: Settings > General > About > Version. On macOS: Apple menu > About This Mac > Overview. On Windows for iTunes/iCloud: Open application and check Help > About.

Verify Fix Applied:

Confirm the software version matches or exceeds the patched versions specified in the fix_official section.

📡 Detection & Monitoring

Log Indicators:

Look for crashes or errors in application logs related to image processing libraries (e.g., CoreGraphics, ImageIO).
Monitor for unusual process creation or network connections after image file access.

Network Indicators:

Detect downloads of suspicious image files from untrusted sources via network traffic analysis.
Monitor for outbound connections from affected applications post-image processing.

SIEM Query:

Example: 'source="application_logs" AND (event="crash" OR error="image_processing") AND device_type IN ("iOS", "macOS", "tvOS", "watchOS")'

📊 Metadata

CVE ID: CVE-2020-9936

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CWE: CWE-787

Published: October 16, 2020

Last Updated: November 21, 2024

🔗 References

https://support.apple.com/HT211288 Release Notes,Vendor Advisory
https://support.apple.com/HT211289 Release Notes,Vendor Advisory
https://support.apple.com/HT211290 Release Notes,Vendor Advisory
https://support.apple.com/HT211291 Release Notes,Vendor Advisory
https://support.apple.com/HT211293 Release Notes,Vendor Advisory
https://support.apple.com/HT211294 Release Notes,Vendor Advisory
https://support.apple.com/HT211295 Release Notes,Vendor Advisory
https://support.apple.com/HT211288 Release Notes,Vendor Advisory
https://support.apple.com/HT211289 Release Notes,Vendor Advisory
https://support.apple.com/HT211290 Release Notes,Vendor Advisory
https://support.apple.com/HT211291 Release Notes,Vendor Advisory
https://support.apple.com/HT211293 Release Notes,Vendor Advisory
https://support.apple.com/HT211294 Release Notes,Vendor Advisory
https://support.apple.com/HT211295 Release Notes,Vendor Advisory

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