Apple WebKit Integer Overflow Remote Code Execution Vulnerability (CVE-2021-30952) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTiOS/iPadOS before 15.2, macOS Monterey before 12.1, Safari before 15.2, tvOS before 15.2, watchOS before 8.3
Processing maliciously crafted web content may lead to arbitrary code execution on the target system.
Immediately apply the official software updates provided by Apple to upgrade to the patched versions.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Use the following commands to check and apply the latest software updates on macOS environments.
# Check and install all available software updates via macOS terminal
sudo softwareupdate --list
sudo softwareupdate --install --all2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted websites and enforce strict content filtering policies via MDM solutions.
# Enable application firewall on macOS to restrict unauthorized incoming connections
sudo defaults write /Library/Preferences/com.apple.alf globalstate -int 1
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.alf.agent.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.alf.agent.plist3. Log Audit & IoC Verification Commands
Run the following script to verify the current macOS and Safari versions to determine vulnerability exposure.
# Script to check macOS system version and Safari application version
echo '=== OS Version ==='
sw_vers
echo '=== Safari Version ==='
/usr/libexec/PlistBuddy -c 'Print CFBundleShortVersionString' /Applications/Safari.app/Contents/Info.plistBlock Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-30952) is an integer overflow flaw (CWE-190) within Apple's WebKit browser engine. The root cause lies in insufficient input validation when processing web content, leading to incorrect memory allocation size calculations during rendering.
2. Exploitation Mechanics & Attack Scenario
An attacker crafts a malicious web page containing specially designed HTML, JavaScript, or media assets. When a user visits this page using Safari or any WebKit-based application (such as mail clients or in-app browsers), the engine processes the malicious payload, triggering an integer overflow. This leads to heap memory corruption, allowing the attacker to execute arbitrary code within the context of the application.
3. Infrastructure & Business Impact
As this vulnerability is listed in the CISA KEV catalog, it has been actively exploited in the wild. Successful exploitation allows attackers to compromise user devices, steal sensitive corporate data, hijack active sessions, and potentially establish a foothold for lateral movement within enterprise networks.
Official Vendor Advisories & References
An integer overflow was addressed with improved input validation. This issue is fixed in tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2 and iPadOS 15.2, watchOS 8.3. Processing maliciously crafted web content may lead to arbitrary code execution.
Frequently Asked SecOps Questions (CVE-2021-30952)
FAQQ1. How critical is CVE-2021-30952 and is it actively exploited in the wild?
CVE-2021-30952 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 7.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-30952?
Primary impacted vendors include apple across safari, ios, ipados, macos, tvos, watchos. Scope summary: iOS < 15.2, iPadOS < 15.2, macOS Monterey < 12.1, Safari < 15.2, tvOS < 15.2, watchOS < 8.3
Q3. What temporary mitigations or workarounds exist for CVE-2021-30952 before patching?
[Mitigation] Immediately apply the official software updates provided by Apple to upgrade to the patched versions. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2021-30952
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