CVE-2020-27918
📋 TL;DR
CVE-2020-27918 is a use-after-free 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 multiple Apple operating systems and applications including macOS, iOS, iPadOS, watchOS, tvOS, Safari, and iCloud for Windows.
💻 Affected Systems
- macOS
- iOS
- iPadOS
- watchOS
- tvOS
- Safari
- iCloud for Windows
- iTunes for Windows
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
Icloud by Apple
Ipados by Apple
Itunes 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 →Safari by Apple
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, allowing data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malicious website delivers exploit payload that executes arbitrary code in browser context, potentially stealing credentials, session cookies, or installing malware.
If Mitigated
With proper patching and security controls, impact is limited to denial of service or browser crash at most.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website) but no authentication. Public references and disclosures suggest exploit code may be available in security research communities.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, tvOS 14.2, Safari 14.0.1, iCloud for Windows 11.5, iTunes 12.11 for Windows
Vendor Advisory: https://support.apple.com/en-us/HT211931
Restart Required: Yes
Instructions:
1. Open System Preferences > Software Update on macOS. 2. Open Settings > General > Software Update on iOS/iPadOS. 3. Open Settings > General > Software Update on watchOS. 4. Open Settings > System > Software Updates on tvOS. 5. For Windows applications, update through Apple Software Update or download latest versions from Apple website.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript in Safari to prevent exploitation through web content
Safari > Preferences > Security > uncheck 'Enable JavaScript'
Use Alternative Browser
allUse browsers not based on WebKit engine until patched
🧯 If You Can't Patch
- Implement web content filtering to block known malicious sites and suspicious JavaScript
- Restrict user access to untrusted websites through proxy or firewall policies
🔍 How to Verify
Check if Vulnerable:
Check current OS/application version against affected versions list. On macOS: About This Mac > Overview. On iOS: Settings > General > About > Version.Check Version:
macOS: sw_vers -productVersion, iOS: Settings > General > About > VersionVerify Fix Applied:
Verify version numbers match or exceed patched versions: macOS 11.0.1+, iOS 14.2+, iPadOS 14.2+, watchOS 7.1+, tvOS 14.2+, Safari 14.0.1+, iCloud for Windows 11.5+, iTunes for Windows 12.11+📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with WebKit process termination
- Unexpected browser extensions or processes
- Suspicious network connections from browser processes
Network Indicators:
- Outbound connections to known exploit hosting domains
- Unusual JavaScript execution patterns in web traffic
SIEM Query:
source="*browser*" AND (event="crash" OR event="process_creation") AND process_name="WebKit"🔗 References
- http://seclists.org/fulldisclosure/2020/Dec/32
- http://www.openwall.com/lists/oss-security/2021/03/22/1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EQ3U3VBSOJB46WCO66TEWE5OAXLTU3YW/
- 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/HT211928
- https://support.apple.com/en-us/HT211929
- https://support.apple.com/en-us/HT211930
- https://support.apple.com/en-us/HT211931
- https://support.apple.com/en-us/HT211933
- https://support.apple.com/en-us/HT211934
- https://support.apple.com/en-us/HT211935
- https://www.debian.org/security/2021/dsa-4877
- http://seclists.org/fulldisclosure/2020/Dec/32
- http://www.openwall.com/lists/oss-security/2021/03/22/1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EQ3U3VBSOJB46WCO66TEWE5OAXLTU3YW/
- 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/HT211928
- https://support.apple.com/en-us/HT211929
- https://support.apple.com/en-us/HT211930
- https://support.apple.com/en-us/HT211931
- https://support.apple.com/en-us/HT211933
- https://support.apple.com/en-us/HT211934
- https://support.apple.com/en-us/HT211935
- https://www.debian.org/security/2021/dsa-4877
