CVE-2020-27930
📋 TL;DR
CVE-2020-27930 is a memory corruption vulnerability in Apple's font processing that allows arbitrary code execution when processing malicious fonts. Attackers can exploit this to run code on affected devices, potentially compromising the entire system. This affects multiple Apple operating systems including macOS, iOS, iPadOS, and watchOS.
💻 Affected Systems
- macOS
- iOS
- iPadOS
- watchOS
- Safari
📦 What is this software?
Ipados by Apple
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 →Watchos by Apple
Watchos by Apple
Watchos by Apple
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the device, enabling data theft, persistence installation, and lateral movement within networks.
Likely Case
Remote code execution leading to malware installation, credential theft, or ransomware deployment on vulnerable Apple devices.
If Mitigated
Limited impact with proper network segmentation and endpoint protection, potentially only affecting isolated systems.
🎯 Exploit Status
Public proof-of-concept exists via Packet Storm. Exploitation requires user interaction (viewing malicious content) but no authentication. Font processing vulnerabilities are commonly exploited in real attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, and security updates for older versions
Vendor Advisory: https://support.apple.com/en-us/HT211928
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update on macOS. 2. Install all available updates. 3. Restart the device when prompted. For iOS/iPadOS: Settings > General > Software Update. For watchOS: Use iPhone Watch app > General > Software Update.
🔧 Temporary Workarounds
Disable automatic font loading in Safari
macosPrevent Safari from automatically loading web fonts which could be malicious
Safari > Preferences > Advanced > uncheck 'Never use font sizes smaller than' (partial mitigation)
Use content filtering
allBlock known malicious domains and font file downloads at network perimeter
🧯 If You Can't Patch
- Segment Apple devices from critical network resources using firewall rules
- Implement application allowlisting to prevent execution of unauthorized binaries
🔍 How to Verify
Check if Vulnerable:
Check system version against patched versions: macOS: About This Mac > Overview; iOS/iPadOS: Settings > General > About > Version; watchOS: Watch app on iPhone > General > About > VersionCheck Version:
macOS: sw_vers -productVersion; iOS/iPadOS: Settings app; watchOS: Watch appVerify Fix Applied:
Verify system version matches or exceeds patched versions listed in Apple advisories📡 Detection & Monitoring
Log Indicators:
- Unexpected font loading processes
- Safari/WebKit crashes with font-related errors
- Unusual process execution following font file access
Network Indicators:
- Downloads of font files from untrusted sources
- Font loading from external domains in web traffic
SIEM Query:
process_name:safari AND (event_type:crash OR cmdline:*font*) OR file_path:*.ttf OR file_path:*.otf AND process_creation🔗 References
- http://packetstormsecurity.com/files/161294/Apple-Safari-Remote-Code-Execution.html
- http://seclists.org/fulldisclosure/2020/Dec/32
- https://support.apple.com/en-us/HT211928
- https://support.apple.com/en-us/HT211929
- https://support.apple.com/en-us/HT211931
- https://support.apple.com/en-us/HT211940
- https://support.apple.com/en-us/HT211944
- https://support.apple.com/en-us/HT211945
- https://support.apple.com/en-us/HT211946
- https://support.apple.com/en-us/HT211947
- http://packetstormsecurity.com/files/161294/Apple-Safari-Remote-Code-Execution.html
- http://seclists.org/fulldisclosure/2020/Dec/32
- https://support.apple.com/en-us/HT211928
- https://support.apple.com/en-us/HT211929
- https://support.apple.com/en-us/HT211931
- https://support.apple.com/en-us/HT211940
- https://support.apple.com/en-us/HT211944
- https://support.apple.com/en-us/HT211945
- https://support.apple.com/en-us/HT211946
- https://support.apple.com/en-us/HT211947
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-27930
