CVE-2021-1789
📋 TL;DR
CVE-2021-1789 is a type confusion vulnerability in Apple's WebKit browser engine that allows arbitrary code execution when processing malicious web content. Attackers can exploit this by tricking users into visiting specially crafted websites, potentially taking full control of affected devices. This affects macOS, iOS, iPadOS, tvOS, watchOS, and Safari users on vulnerable versions.
💻 Affected Systems
- Safari
- WebKit
- iOS
- iPadOS
- macOS
- tvOS
- watchOS
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
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 →Tvos by Apple
Watchos by Apple
Webkitgtk by Webkitgtk
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the device, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Browser-based compromise leading to session hijacking, credential theft, or installation of malware through drive-by download attacks.
If Mitigated
Limited impact with proper sandboxing and security controls preventing privilege escalation or lateral movement.
🎯 Exploit Status
Type confusion vulnerabilities in WebKit are frequently exploited in the wild. While no public PoC exists, similar vulnerabilities have been weaponized for targeted attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, tvOS 14.4, watchOS 7.3, iOS 14.4, iPadOS 14.4, Safari 14.0.3
Vendor Advisory: https://support.apple.com/en-us/HT212146
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update. 2. Install all available updates. 3. Restart the device when prompted. 4. For Safari, update through the App Store or System Preferences.
🔧 Temporary Workarounds
Browser Restrictions
allDisable JavaScript or use browser extensions to block untrusted websites
Network Filtering
allBlock access to known malicious domains and implement web content filtering
🧯 If You Can't Patch
- Implement strict web content filtering and block access to untrusted websites
- Use application whitelisting to prevent unauthorized code execution
🔍 How to Verify
Check if Vulnerable:
Check system version: macOS - About This Mac; iOS/iPadOS - Settings > General > About; Safari - Safari > About SafariCheck Version:
macOS: sw_vers; iOS: Settings > General > About; Safari: defaults read /Applications/Safari.app/Contents/Info.plist CFBundleShortVersionStringVerify Fix Applied:
Verify system version matches or exceeds patched versions listed in vendor advisory📡 Detection & Monitoring
Log Indicators:
- Unusual Safari/WebKit process crashes
- Suspicious JavaScript execution patterns
- Unexpected network connections from browser processes
Network Indicators:
- Connections to known malicious domains from browser processes
- Unusual outbound traffic patterns following web browsing
SIEM Query:
process_name:Safari OR process_name:WebKit AND (event_type:crash OR suspicious_network_activity)🔗 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
