CVE-2021-30953 – This vulnerability allows attackers to execute ... (How to Fix)

Q: What is the severity of CVE-2021-30953?

CVE-2021-30953 has a CVSS score of 8.8 (HIGH). This vulnerability allows attackers to execute arbitrary code on affected Apple devices by tricking users into visiting malicious web pages. It affects Safari browsers and Apple operating systems before specific patched versions. Users who haven't updated their Apple devices are vulnerable to this remote code execution attack.

📋 TL;DR

This vulnerability allows attackers to execute arbitrary code on affected Apple devices by tricking users into visiting malicious web pages. It affects Safari browsers and Apple operating systems before specific patched versions. Users who haven't updated their Apple devices are vulnerable to this remote code execution attack.

💻 Affected Systems

Products:

Safari
tvOS
macOS Monterey
iOS
iPadOS
watchOS

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

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

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations of affected versions are vulnerable when processing web content through Safari or WebKit 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

Complete system compromise leading to data theft, ransomware deployment, or persistent backdoor installation on affected devices.

🟠

Likely Case

Malicious actors create fake websites that exploit this vulnerability to install malware, steal credentials, or hijack user sessions.

🟢

If Mitigated

With proper patching, the vulnerability is eliminated; with network filtering, the risk is reduced but not eliminated for unpatched systems.

🌐 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. The out-of-bounds read can lead to memory corruption enabling code execution.

🛠️ 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 Preferences (macOS) or Settings (iOS/iPadOS/tvOS/watchOS). 2. Navigate to Software Update. 3. Install the latest available update. 4. Restart the device when prompted.

🔧 Temporary Workarounds

Web Content Filtering

all

Block access to untrusted websites using network filtering or browser extensions to prevent exposure to malicious content.

Disable JavaScript

all

Temporarily disable JavaScript in Safari settings to mitigate the vulnerability (breaks most websites).

🧯 If You Can't Patch

Implement strict web filtering to block access to untrusted websites
Use alternative browsers that are not based on WebKit until patching is possible

🔍 How to Verify

Check if Vulnerable:

Check the operating system version: On macOS, go to Apple menu > About This Mac; on iOS/iPadOS, go to Settings > General > About; compare against patched versions.

Check Version:

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

Verify Fix Applied:

Verify the installed version matches or exceeds: tvOS 15.2, macOS Monterey 12.1, Safari 15.2, iOS 15.2, iPadOS 15.2, watchOS 8.3

📡 Detection & Monitoring

Log Indicators:

Unusual Safari/WebKit process crashes
Memory access violation logs in system logs
Unexpected network connections from Safari processes

Network Indicators:

Outbound connections to suspicious domains following web browsing
Unusual HTTP traffic patterns from Apple devices

SIEM Query:

source="apple_system_logs" AND (process="Safari" OR process="WebKit") AND (event="crash" OR event="memory_violation")

📊 Metadata

CVE ID: CVE-2021-30953

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-125

Published: August 24, 2021

Last Updated: November 21, 2024

🔗 References

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🔗 Related Vulnerabilities

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