Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability (CVE-2021-1870, CISA KEV)
Executive & SecOps Summary
SECOPS ASSESSMENTApple iOS before 14.4, iPadOS before 14.4, macOS Big Sur before 11.2, and macOS Catalina/Mojave prior to Security Update 2021-001.
A remote attacker can execute arbitrary code on the target device via malicious web content, bypassing sandbox restrictions. This vulnerability has been actively exploited in the wild.
Immediately apply the official software updates provided by Apple to upgrade to iOS/iPadOS 14.4, macOS Big Sur 11.2, or later.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update all Apple devices to the latest available operating system versions immediately. For enterprise macOS fleets, administrators can force updates using the following command:
# Check and force install all pending macOS software updates and restart
sudo softwareupdate --install --all --restart2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted websites. Administrators can deploy MDM configuration profiles to disable JavaScript or restrict browser capabilities on managed devices.
<!-- MDM Configuration Profile Snippet: Disable Safari JavaScript -->
<key>javascriptEnabled</key>
<false/>3. Log Audit & IoC Verification Commands
Verify the current operating system and WebKit framework versions to identify vulnerable assets within your infrastructure.
# Query the current macOS version and build details
sw_vers
# Check the specific WebKit framework version installed on the system
plutil -extract CFBundleVersion raw /System/Library/Frameworks/WebKit.framework/Resources/Info.plistBlock 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-2021-1870) is a critical logic issue within the WebKit browser engine used by Apple operating systems. Due to improper state restrictions and type handling during JIT (Just-In-Time) compilation, a type confusion or logic flaw can be triggered. Apple addressed this issue by implementing improved restrictions on object states and execution paths.
2. Exploitation Mechanics & Attack Scenario
An attacker crafts a malicious web page containing specialized JavaScript designed to exploit the WebKit logic flaw. When a user visits this page using Safari or any application utilizing the WebKit rendering engine, the engine misinterprets object types during compilation. This grants the attacker arbitrary memory read/write capabilities, leading to arbitrary code execution within the context of the sandboxed browser process.
3. Infrastructure & Business Impact
As a zero-day vulnerability actively exploited in the wild, this flaw poses a severe threat to enterprise environments. Successful exploitation allows attackers to compromise corporate mobile devices and workstations, potentially leading to credential theft, lateral movement within internal networks, and unauthorized access to sensitive business data.
Official Vendor Advisories & References
A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
Frequently Asked SecOps Questions (CVE-2021-1870)
FAQQ1. How critical is CVE-2021-1870 and is it actively exploited in the wild?
CVE-2021-1870 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 7.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-1870?
Primary impacted vendors include apple across safari, webkit, ios, ipados, macos. Scope summary: Apple iOS and iPadOS versions prior to 14.4, macOS Big Sur versions prior to 11.2, and macOS Catalina/Mojave prior to Security Update 2021-001
Q3. What temporary mitigations or workarounds exist for CVE-2021-1870 before patching?
[Mitigation] Immediately apply the official software updates provided by Apple to upgrade to iOS/iPadOS 14.4, macOS Big Sur 11.2, or later. 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-2021-1870
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
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