Apple WebKit Integer Overflow Remote Code Execution Vulnerability (CVE-2021-30663) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTApple devices running versions prior to iOS 14.5, iPadOS 14.5, macOS Big Sur 11.3, tvOS 14.6, and Safari 14.1.1
Processing maliciously crafted web content may lead to arbitrary code execution (RCE) on the target device
Immediately apply the official software updates provided by Apple (iOS 14.5.1, macOS 11.3.1, or later)
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update Apple devices to the latest secure versions. For macOS administrators managing fleets via terminal or MDM, use the following commands to check and apply updates:
# List all available software updates
softwareupdate -l
# Download and install all critical updates and restart the system
sudo softwareupdate -i -a --restart2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted external websites and enforce strict web filtering policies. Block known malicious domains at the perimeter firewall or proxy level.
# Temporary domain blocking on macOS via hosts file
echo '127.0.0.1 malicious-domain-to-block.com' | sudo tee -a /etc/hosts3. Log Audit & IoC Verification Commands
Use the following script to audit the current macOS and Safari versions to identify vulnerable endpoints:
#!/bin/bash
# Audit script for macOS and Safari versions
echo '[*] Checking macOS System Version...'
sw_vers
echo '[*] Checking Safari Browser Version...'
if [ -d '/Applications/Safari.app' ]; then
defaults read /Applications/Safari.app/Contents/Info.plist BundleShortVersionString
else
echo '[-] Safari is not found in the default directory.'
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-30663) is an integer overflow issue (CWE-190) residing within Apple's WebKit rendering engine. The root cause lies in insufficient input validation when processing web content, leading to incorrect memory allocation size calculations during data parsing.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by hosting a specially crafted web page containing malicious HTML, JavaScript, or media assets. When a victim visits the malicious site using Safari or any application utilizing the WebKit framework, the engine triggers an integer overflow. This leads to heap memory corruption, allowing the attacker to bypass sandbox restrictions and execute arbitrary code in the context of the browser process.
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA KEV catalog, this flaw has been actively exploited in the wild. Unpatched corporate endpoints (MacBooks, iPhones, iPads) represent a significant risk, as simple web browsing can serve as an initial entry point for threat actors to compromise devices, exfiltrate sensitive corporate data, and pivot into internal networks.
Official Vendor Advisories & References
An integer overflow was addressed with improved input validation. This issue is fixed in iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, Safari 14.1.1, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution.
Frequently Asked SecOps Questions (CVE-2021-30663)
FAQQ1. How critical is CVE-2021-30663 and is it actively exploited in the wild?
CVE-2021-30663 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 3.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-30663?
Primary impacted vendors include apple across safari, iphone_os, ipados, tvos, macos. Scope summary: Systems running versions prior to iOS 14.5.1, iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, Safari 14.1.1, and macOS Big Sur 11.3.1
Q3. What temporary mitigations or workarounds exist for CVE-2021-30663 before patching?
[Mitigation] Immediately apply the official software updates provided by Apple (iOS 14.5.1, macOS 11.3.1, or later) Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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🔗 Related Advisories in Similar Stack (apple)
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