CVE-2021-30951 – This is a use-after-free vulnerability in Apple... (How to Fix)

Q: What is the severity of CVE-2021-30951?

CVE-2021-30951 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Apple's WebKit browser engine that could allow arbitrary code execution when processing malicious web content. It affects Safari browser and Apple operating systems including iOS, macOS, tvOS, and watchOS. Attackers could exploit this by tricking users into visiting specially crafted malicious websites.

📋 TL;DR

This is a use-after-free vulnerability in Apple's WebKit browser engine that could allow arbitrary code execution when processing malicious web content. It affects Safari browser and Apple operating systems including iOS, macOS, tvOS, and watchOS. Attackers could exploit this by tricking users into visiting specially crafted malicious websites.

💻 Affected Systems

Products:

Safari
iOS
iPadOS
macOS
tvOS
watchOS

Versions: Versions prior to tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2, iPadOS 15.2, watchOS 8.3

Operating Systems: iOS, iPadOS, macOS, tvOS, watchOS

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations of affected Apple products are vulnerable. The vulnerability is in WebKit, which powers Safari and other Apple web-rendering components.

📦 What is this software?

Macos by Apple

macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...

Learn more about Macos →

Safari by Apple

View all CVEs affecting Safari →

Tvos by Apple

View all CVEs affecting Tvos →

Watchos by Apple

View all CVEs affecting Watchos →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full system compromise with attacker gaining complete control over the affected device, allowing data theft, ransomware deployment, or persistent backdoor installation.

🟠

Likely Case

Remote code execution in browser context leading to session hijacking, credential theft, or malware installation through drive-by download attacks.

🟢

If Mitigated

Limited impact with proper sandboxing and memory protection features, potentially restricted to browser process only.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires user interaction (visiting malicious website) but no authentication. Use-after-free vulnerabilities typically require precise memory manipulation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2, iPadOS 15.2, watchOS 8.3

Vendor Advisory: https://support.apple.com/en-us/HT212975

Restart Required: Yes

Instructions:

1. Open System Settings/Preferences 2. Navigate to Software Update 3. Install available updates 4. Restart device when prompted

🔧 Temporary Workarounds

Browser Restrictions

all

Disable JavaScript execution in Safari or use alternative browsers until patched

Network Filtering

all

Block access to untrusted websites using web proxy or firewall rules

🧯 If You Can't Patch

Implement strict web content filtering to block malicious sites
Use application whitelisting to prevent unauthorized code execution

🔍 How to Verify

Check if Vulnerable:

Check current OS/browser version against affected versions list

Check Version:

macOS: sw_vers -productVersion; iOS: Settings > General > About > Version; Safari: Safari > About Safari

Verify Fix Applied:

Verify OS/browser version matches or exceeds patched versions

📡 Detection & Monitoring

Log Indicators:

Safari/WebKit crash logs with memory access violations
Unexpected process spawns from browser processes

Network Indicators:

Connections to suspicious domains followed by unusual outbound traffic

SIEM Query:

process_name:Safari AND (event_type:crash OR parent_process:Safari)

📊 Metadata

CVE ID: CVE-2021-30951

CVSS v3 Score: 8.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CWE: CWE-416

Published: August 24, 2021

Last Updated: November 21, 2024

🔗 References

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🔗 Related Vulnerabilities

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