Apple WebKit Memory Corruption Remote Code Execution Vulnerability (CVE-2021-30665) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTApple WebKit engine in versions prior to iOS 14.5.1, iPadOS 14.5.1, macOS Big Sur 11.3.1, watchOS 7.4.1, and tvOS 14.6
Processing maliciously crafted web content may lead to arbitrary code execution, with active exploitation reported in the wild
Immediately update Apple operating systems to the latest patched versions (iOS 14.5.1, macOS 11.3.1, or later) using official software update channels
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the official software updates via the system settings on Apple devices or enforce updates enterprise-wide using an MDM solution.
To check and apply updates via the terminal on macOS, execute the following commands:
# List available software updates
softwareupdate -l
# Download and install all critical security and OS updates immediately
sudo softwareupdate -iaR2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted external websites and enforce strict email/message filtering to prevent users from clicking suspicious links. Restrict unauthorized browser usage via MDM policies.
# Verify and enable the macOS Application Layer Firewall
sudo defaults write /Library/Preferences/com.apple.alf globalstate -int 1
sudo launchctl load /System/Library/LaunchDaemons/com.apple.alf.agent.plist3. Log Audit & IoC Verification Commands
Use the following script to audit the current operating system version and identify if the system is running a vulnerable version.
# Script to check current macOS version and alert if vulnerable
os_version=$(sw_vers -productVersion)
echo 'Current macOS Version:' $os_version
# Check vulnerability status for macOS Big Sur (11.x)
if [[ $os_version == 11.* ]]; then
major=$(echo $os_version | cut -d. -f1)
minor=$(echo $os_version | cut -d. -f2)
patch=$(echo $os_version | cut -d. -f3)
if [ $minor -lt 3 ] || ([ $minor -eq 3 ] && [ -z '$patch' ]); then
echo '[WARNING] This system is vulnerable to CVE-2021-30665. Please update immediately.'
else
echo '[INFO] System is patched or running a newer minor version.'
fi
fiBlock Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-30665) is a critical memory corruption issue within Apple's WebKit rendering engine. The root cause lies in inadequate state management during the processing of web content. Due to improper validation of object lifecycles or state transitions, the engine is susceptible to out-of-bounds writes (CWE-787) or use-after-free conditions, leading to memory corruption.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by hosting a specially crafted web page containing malicious HTML, JavaScript, or CSS. When a target user visits the malicious site via Safari or any application utilizing the WebKit framework, the engine fails to manage internal states correctly while parsing the content. This corrupts the heap memory, allowing the attacker to manipulate the memory layout, hijack the execution flow, and execute arbitrary shellcode within the context of the WebKit sandbox.
3. Infrastructure & Business Impact
As this vulnerability is listed in the CISA KEV catalog and has been actively exploited in the wild, it poses an immediate threat to enterprise environments. Successful exploitation on employee devices (iPhones, iPads, Macs) can lead to complete device compromise via simple web browsing. This serves as an entry point for lateral movement, credential harvesting, and sensitive corporate data exfiltration.
Official Vendor Advisories & References
A memory corruption issue was addressed with improved state management. This issue is fixed in watchOS 7.4.1, iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
Frequently Asked SecOps Questions (CVE-2021-30665)
FAQQ1. How critical is CVE-2021-30665 and is it actively exploited in the wild?
CVE-2021-30665 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 3.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-30665?
Primary impacted vendors include apple across webkit, safari, ios, ipados, macos, watchos, tvos. Scope summary: Apple iOS and iPadOS prior to 14.5.1, macOS Big Sur prior to 11.3.1, watchOS prior to 7.4.1, tvOS prior to 14.6, and iOS prior to 12.5.3
Q3. What temporary mitigations or workarounds exist for CVE-2021-30665 before patching?
[Mitigation] Immediately update Apple operating systems to the latest patched versions (iOS 14.5.1, macOS 11.3.1, or later) using official software update channels 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-2021-30665
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (apple)
View Category →Apple iOS, macOS, and watchOS Memory Corruption Arbitrary Code Execution Vulnerability (CVE-2026-20700)
[Affected Scope] Apple devices running iOS before 26.3, iPadOS before 26.3, macOS Tahoe before 26.3, tvOS before 26.3, visionOS before 26.3, and watchOS before 26.3
Apple iOS and macOS Out-of-bounds Write Remote Code Execution Vulnerability (CVE-2026-86950) Security Advisory
[Affected Scope] All Apple devices running versions prior to iOS 18.7.11/26.7.1 and macOS Sequoia 15.8.1/Tahoe 26.7.1.
Apple macOS Screen Sharing Authentication Bypass Vulnerability (CVE-2026-65400)
[Affected Scope] macOS systems running versions prior to Sequoia 15.7.9, Sonoma 14.8.9, Tahoe 26.6.1/26.7, or Golden Gate 27 with Screen Sharing or VNC services enabled
Google Chrome Skia Graphics Engine Out-of-bounds Write Vulnerability (CVE-2026-3909) Technical Advisory
[Affected Scope] Google Chrome and Chromium-based browsers prior to version 146.0.7680.75
Subscribe to Daily Vulnerability Briefings & KEV Alerts
Concise morning briefings for SecOps, DevSecOps, and SRE teams covering newly exploited CVEs and mitigation priorities.