CVE-2021-30858
📋 TL;DR
This is a use-after-free vulnerability in Apple's WebKit browser engine that allows arbitrary code execution when processing malicious web content. It affects iOS, iPadOS, and macOS systems and was reportedly actively exploited in the wild before patching.
💻 Affected Systems
- iOS
- iPadOS
- macOS
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the device, enabling data theft, surveillance, or ransomware deployment.
Likely Case
Remote code execution leading to malware installation, credential theft, or device takeover when users visit malicious websites.
If Mitigated
No impact if systems are fully patched or if web content filtering blocks malicious sites.
🎯 Exploit Status
Apple confirmed active exploitation in the wild. Exploitation requires user interaction (visiting malicious website).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: iOS 14.8, iPadOS 14.8, macOS Big Sur 11.6
Vendor Advisory: https://support.apple.com/en-us/HT212804
Restart Required: Yes
Instructions:
1. Go to Settings > General > Software Update. 2. Download and install iOS 14.8/iPadOS 14.8/macOS Big Sur 11.6. 3. Restart device after installation completes.
🔧 Temporary Workarounds
Disable JavaScript
macosTemporarily disable JavaScript in Safari to prevent exploitation via malicious web content.
Safari > Preferences > Security > Uncheck 'Enable JavaScript'
Use Alternative Browser
allUse non-WebKit browsers like Firefox or Chrome until patching is complete.
🧯 If You Can't Patch
- Implement strict web content filtering to block known malicious sites
- Restrict device internet access to essential services only
🔍 How to Verify
Check if Vulnerable:
Check iOS/iPadOS version in Settings > General > About > Version. Check macOS version in Apple menu > About This Mac.Check Version:
sw_vers (macOS) or Settings app (iOS/iPadOS)Verify Fix Applied:
Verify version is iOS 14.8+, iPadOS 14.8+, or macOS Big Sur 11.6+.📡 Detection & Monitoring
Log Indicators:
- Unusual Safari/WebKit process crashes
- Suspicious web content processing
Network Indicators:
- Connections to known malicious domains serving exploit code
SIEM Query:
process_name:safari AND event_type:crash OR destination_ip IN (malicious_ip_list)🔗 References
- http://seclists.org/fulldisclosure/2021/Sep/25
- http://seclists.org/fulldisclosure/2021/Sep/27
- http://seclists.org/fulldisclosure/2021/Sep/29
- http://seclists.org/fulldisclosure/2021/Sep/38
- http://seclists.org/fulldisclosure/2021/Sep/39
- http://seclists.org/fulldisclosure/2021/Sep/50
- http://www.openwall.com/lists/oss-security/2021/09/20/1
- http://www.openwall.com/lists/oss-security/2021/10/26/9
- http://www.openwall.com/lists/oss-security/2021/10/27/1
- http://www.openwall.com/lists/oss-security/2021/10/27/2
- http://www.openwall.com/lists/oss-security/2021/10/27/4
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BO6DMTHZR57JDBOXPSNR2MKDMCRWV265/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XYNV7ASK4LQVAUMJXNXBS3Z7RVDQ2N3W/
- https://support.apple.com/en-us/HT212804
- https://support.apple.com/en-us/HT212807
- https://support.apple.com/kb/HT212824
- https://www.debian.org/security/2021/dsa-4975
- https://www.debian.org/security/2021/dsa-4976
- http://seclists.org/fulldisclosure/2021/Sep/25
- http://seclists.org/fulldisclosure/2021/Sep/27
- http://seclists.org/fulldisclosure/2021/Sep/29
- http://seclists.org/fulldisclosure/2021/Sep/38
- http://seclists.org/fulldisclosure/2021/Sep/39
- http://seclists.org/fulldisclosure/2021/Sep/50
- http://www.openwall.com/lists/oss-security/2021/09/20/1
- http://www.openwall.com/lists/oss-security/2021/10/26/9
- http://www.openwall.com/lists/oss-security/2021/10/27/1
- http://www.openwall.com/lists/oss-security/2021/10/27/2
- http://www.openwall.com/lists/oss-security/2021/10/27/4
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BO6DMTHZR57JDBOXPSNR2MKDMCRWV265/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XYNV7ASK4LQVAUMJXNXBS3Z7RVDQ2N3W/
- https://support.apple.com/en-us/HT212804
- https://support.apple.com/en-us/HT212807
- https://support.apple.com/kb/HT212824
- https://www.debian.org/security/2021/dsa-4975
- https://www.debian.org/security/2021/dsa-4976
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30858
