CVE-2021-30851
📋 TL;DR
CVE-2021-30851 is a memory corruption vulnerability in Apple's WebKit browser engine that could allow remote code execution when processing malicious web content. This affects users of Safari, iOS, iPadOS, tvOS, and watchOS. Attackers could exploit this by tricking users into visiting specially crafted websites.
💻 Affected Systems
- Safari
- iOS
- iPadOS
- 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 →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
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining arbitrary code execution at the user's privilege level, potentially leading to data theft, ransomware deployment, or persistent access.
Likely Case
Browser compromise leading to session hijacking, credential theft, or installation of malware on the affected device.
If Mitigated
Limited impact with browser sandboxing potentially containing the exploit, though sandbox escapes are possible.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website). Public proof-of-concept exists in security mailing lists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Safari 15, iOS 15, iPadOS 15, tvOS 15, watchOS 8
Vendor Advisory: https://support.apple.com/en-us/HT212814
Restart Required: Yes
Instructions:
1. Update to Safari 15 on macOS. 2. Update iOS/iPadOS devices to version 15 or later. 3. Update tvOS to version 15 or later. 4. Update watchOS to version 8 or later. 5. Restart devices after update.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript in Safari to prevent exploitation, though this breaks most websites.
Safari > Preferences > Security > Uncheck 'Enable JavaScript'
Use Alternative Browser
allUse a non-WebKit based browser until patches are applied.
🧯 If You Can't Patch
- Implement network filtering to block known malicious domains and restrict web browsing to trusted sites only.
- Use application whitelisting to prevent execution of unauthorized binaries that could be dropped by the exploit.
🔍 How to Verify
Check if Vulnerable:
Check Safari version: Safari > About Safari. For iOS/iPadOS: Settings > General > About > Version. For tvOS: Settings > General > About > Version. For watchOS: iPhone Watch app > General > About > Version.Check Version:
Safari: Not applicable via command line. iOS: Not applicable via command line. Use GUI methods above.Verify Fix Applied:
Confirm version is Safari 15+, iOS 15+, iPadOS 15+, tvOS 15+, or watchOS 8+.📡 Detection & Monitoring
Log Indicators:
- Unusual browser crashes, unexpected process creation from browser processes, suspicious network connections from browser to unknown domains
Network Indicators:
- Traffic to known exploit domains, unusual outbound connections following web browsing
SIEM Query:
source="browser_logs" AND (event="crash" OR process="unexpected_child") OR dest_ip IN (malicious_ip_list)🔗 References
- http://www.openwall.com/lists/oss-security/2021/10/31/1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/H6MGXCX7P5AHWOQ6IRT477UKT7IS4DAD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ON5SDVVPVPCAGFPW2GHYATZVZYLPW2L4/
- https://support.apple.com/en-us/HT212814
- https://support.apple.com/en-us/HT212815
- https://support.apple.com/en-us/HT212816
- https://support.apple.com/en-us/HT212819
- https://support.apple.com/kb/HT212869
- https://www.debian.org/security/2021/dsa-4995
- https://www.debian.org/security/2021/dsa-4996
- http://www.openwall.com/lists/oss-security/2021/10/31/1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/H6MGXCX7P5AHWOQ6IRT477UKT7IS4DAD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ON5SDVVPVPCAGFPW2GHYATZVZYLPW2L4/
- https://support.apple.com/en-us/HT212814
- https://support.apple.com/en-us/HT212815
- https://support.apple.com/en-us/HT212816
- https://support.apple.com/en-us/HT212819
- https://support.apple.com/kb/HT212869
- https://www.debian.org/security/2021/dsa-4995
- https://www.debian.org/security/2021/dsa-4996
