CVE-2020-27911 – CVE-2020-27911 is an integer overflow vulnerabi... (How to Fix)

Q: What is the severity of CVE-2020-27911?

CVE-2020-27911 has a CVSS score of 7.8 (HIGH). CVE-2020-27911 is an integer overflow vulnerability in Apple operating systems that could allow a remote attacker to crash applications or execute arbitrary code. This affects macOS, iOS, iPadOS, watchOS, tvOS, and iCloud for Windows users running vulnerable versions. The vulnerability stems from improper input validation that can lead to memory corruption.

📋 TL;DR

CVE-2020-27911 is an integer overflow vulnerability in Apple operating systems that could allow a remote attacker to crash applications or execute arbitrary code. This affects macOS, iOS, iPadOS, watchOS, tvOS, and iCloud for Windows users running vulnerable versions. The vulnerability stems from improper input validation that can lead to memory corruption.

💻 Affected Systems

Products:

macOS
iOS
iPadOS
watchOS
tvOS
iCloud for Windows
iTunes for Windows

Versions: Versions prior to macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, tvOS 14.2, iCloud for Windows 11.5, iTunes 12.11 for Windows

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

Default Config Vulnerable: ⚠️ Yes

Notes: All standard configurations of affected Apple operating systems are vulnerable. The vulnerability is in core system components.

📦 What is this software?

Macos by Apple

macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...

Learn more about Macos →

Tvos by Apple

View all CVEs affecting Tvos →

Watchos by Apple

View all CVEs affecting Watchos →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with full system compromise, allowing attacker to install malware, steal data, or create persistent access.

🟠

Likely Case

Application crashes leading to denial of service, with potential for limited code execution in specific contexts.

🟢

If Mitigated

Minimal impact if systems are patched or isolated from untrusted network sources.

🌐 Internet-Facing: MEDIUM - Requires attacker to deliver malicious input, but can be exploited remotely without authentication.

🏢 Internal Only: LOW - Primarily affects client devices rather than internal servers, though lateral movement is possible if exploited.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploit details are publicly available in Full Disclosure mailing list archives. The integer overflow can be triggered remotely via malicious input.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, tvOS 14.2, iCloud for Windows 11.5, iTunes 12.11 for Windows

Vendor Advisory: https://support.apple.com/en-us/HT211928

Restart Required: Yes

Instructions:

1. Open System Preferences > Software Update on Apple devices. 2. Install all available updates. 3. For Windows applications, update via Apple Software Update or download latest versions from Apple website. 4. Restart devices after installation.

🔧 Temporary Workarounds

Network segmentation

all

Restrict network access to affected devices from untrusted sources

Application control

all

Use application whitelisting to prevent execution of unauthorized code

🧯 If You Can't Patch

Isolate affected systems from internet and untrusted networks
Implement strict network monitoring for unusual activity from these devices

🔍 How to Verify

Check if Vulnerable:

Check system version: On macOS, go to Apple menu > About This Mac. On iOS/iPadOS, go to Settings > General > About. Compare with patched versions listed in advisory.

Check Version:

macOS: sw_vers -productVersion, iOS/iPadOS: Settings > General > About > Version

Verify Fix Applied:

Confirm system version matches or exceeds patched versions listed in affected systems section.

📡 Detection & Monitoring

Log Indicators:

Application crashes with memory corruption errors
Unexpected process termination in system logs

Network Indicators:

Unusual network connections from Apple devices to unknown external IPs
Suspicious inbound traffic patterns

SIEM Query:

source="apple_system_logs" AND (event_type="crash" OR event_type="memory_error") AND device_version<"11.0.1"

📊 Metadata

CVE ID: CVE-2020-27911

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-190

Published: December 8, 2020

Last Updated: November 21, 2024

🔗 References

http://seclists.org/fulldisclosure/2020/Dec/26 Mailing List,Third Party Advisory
http://seclists.org/fulldisclosure/2020/Dec/32 Mailing List,Third Party Advisory
https://support.apple.com/en-us/HT211928 Vendor Advisory
https://support.apple.com/en-us/HT211929 Vendor Advisory
https://support.apple.com/en-us/HT211930 Vendor Advisory
https://support.apple.com/en-us/HT211931 Vendor Advisory
https://support.apple.com/en-us/HT211933 Vendor Advisory
https://support.apple.com/en-us/HT211935 Vendor Advisory
https://support.apple.com/kb/HT212011 Vendor Advisory
http://seclists.org/fulldisclosure/2020/Dec/26 Mailing List,Third Party Advisory
http://seclists.org/fulldisclosure/2020/Dec/32 Mailing List,Third Party Advisory
https://support.apple.com/en-us/HT211928 Vendor Advisory
https://support.apple.com/en-us/HT211929 Vendor Advisory
https://support.apple.com/en-us/HT211930 Vendor Advisory
https://support.apple.com/en-us/HT211931 Vendor Advisory
https://support.apple.com/en-us/HT211933 Vendor Advisory
https://support.apple.com/en-us/HT211935 Vendor Advisory
https://support.apple.com/kb/HT212011 Vendor Advisory

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🔗 Related Vulnerabilities

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