Apple iOS WebKit Memory Corruption Remote Code Execution Vulnerability (CVE-2021-30761)
Executive & SecOps Summary
SECOPS ASSESSMENTApple devices running iOS versions prior to 12.5.4 (including iPhone 5s, iPhone 6, iPad Air, iPad mini 2, iPad mini 3, and iPod touch 6th generation)
Processing maliciously crafted web content may allow remote attackers to trigger memory corruption and execute arbitrary code with system privileges
Immediately update affected devices to iOS 12.5.4 or later to remediate the vulnerability
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Users must update their devices to iOS 12.5.4 or later via Over-the-Air (OTA) updates or by connecting the device to a computer.
# On-device update path:
# Go to Settings -> General -> Software Update -> Download and Install iOS 12.5.4 or later2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted websites and enforce strict web filtering policies via MDM or secure web gateways.
# Example: Block outbound traffic to suspicious external domains at the network gateway level
# (Apply on corporate proxy or DNS filtering systems)
iptables -A FORWARD -p tcp --dport 443 -m string --string 'untrusted-exploit-node.com' --algo bm -j DROP3. Log Audit & IoC Verification Commands
Use MDM APIs or asset management tools to query and audit the OS versions of all enrolled iOS devices to identify vulnerable assets.
# Shell script to query MDM API and filter out vulnerable iOS devices running versions below 12.5.4
curl -s -H 'Authorization: Bearer YOUR_MDM_API_TOKEN' https://mdm.internal/api/devices | \
jq '.devices | select(.os_version | test("^12\\.([0-4]\\.|5\\.[0-3])$")) | {device: .device_name, os: .os_version}'Block 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-2021-30761) is a critical memory corruption issue residing in the WebKit rendering engine of Apple iOS. The root cause is improper state management within WebKit when handling specific web resources. This flaw allows an attacker to corrupt memory (CWE-787) during the parsing or rendering of malicious web content, leading to unstable application states or arbitrary code execution.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by hosting a specially crafted web page containing malicious HTML/JavaScript. When a target user visits this page using Safari or any application utilizing the WebKit framework, the engine processes the malicious payload. Due to the state management flaw, the engine writes data outside the intended memory boundaries, allowing the attacker to hijack the control flow and execute arbitrary shellcode within the context of the WebKit process. This vulnerability has been actively exploited in the wild.
3. Infrastructure & Business Impact
Successful exploitation of this vulnerability grants the attacker remote code execution capabilities on the target mobile device. In an enterprise environment, this can serve as an initial entry point, enabling attackers to bypass sandbox restrictions, escalate privileges, and compromise sensitive corporate data, credentials, and internal network communications.
Official Vendor Advisories & References
A memory corruption issue was addressed with improved state management. This issue is fixed in iOS 12.5.4. 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-2021-30761)
FAQQ1. How critical is CVE-2021-30761 and is it actively exploited in the wild?
CVE-2021-30761 is rated CVSS 8.8 (HIGH) with a 30-day EPSS exploitation probability of 10.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-30761?
Primary impacted vendors include apple across ios, safari, webkit. Scope summary: Apple iOS devices running versions prior to 12.5.4 (iPhone 5s, iPhone 6, iPhone 6 Plus, iPad Air, iPad mini 2, iPad mini 3, and iPod touch 6th generation)
Q3. What temporary mitigations or workarounds exist for CVE-2021-30761 before patching?
[Mitigation] Immediately update affected devices to iOS 12.5.4 or later to remediate the vulnerability 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-2021-30761
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🔗 Related Advisories in Similar Stack (apple)
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