CVE-2021-30665: Apple iPadOS RCE Vulnerability

CVE-2021-30665 Overview

CVE-2021-30665 is a memory corruption vulnerability affecting Apple's WebKit browser engine. The vulnerability arises from improper state management, allowing an attacker to craft malicious web content that, when processed by a vulnerable device, can lead to arbitrary code execution. This vulnerability affects a wide range of Apple products including iOS, iPadOS, macOS, tvOS, and watchOS.

Apple has acknowledged that this vulnerability has been actively exploited in the wild, and it has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog, underscoring its severity and the urgency of applying patches.

Critical Impact

This memory corruption vulnerability enables arbitrary code execution through maliciously crafted web content and has been confirmed as actively exploited in the wild.

Affected Products

• Apple iOS (versions prior to 14.5.1 and 12.5.3)
• Apple iPadOS (versions prior to 14.5.1)
• Apple macOS Big Sur (versions prior to 11.3.1)
• Apple tvOS (versions prior to 14.6)
• Apple watchOS (versions prior to 7.4.1)

Discovery Timeline

• 2021-09-08 - CVE-2021-30665 published to NVD
• 2025-10-23 - Last updated in NVD database

Technical Details for CVE-2021-30665

Vulnerability Analysis

CVE-2021-30665 is classified as CWE-787 (Out-of-Bounds Write), a memory corruption vulnerability within Apple's WebKit engine. The root issue lies in improper state management during the processing of web content. When a user navigates to a malicious webpage or encounters crafted web content, the vulnerability can be triggered, corrupting memory and potentially allowing an attacker to execute arbitrary code on the victim's device.

The vulnerability is particularly dangerous because it can be exploited remotely via the network. An attacker only needs to convince a victim to visit a malicious website or interact with compromised web content. Once triggered, the attacker can gain control of the affected device, potentially accessing sensitive data, installing malware, or performing other malicious actions.

Root Cause

The vulnerability stems from improper state management within WebKit's memory handling routines. When processing certain types of web content, the WebKit engine fails to properly validate and manage memory states, leading to an out-of-bounds write condition. This memory corruption can be leveraged by attackers to overwrite critical memory regions and redirect code execution flow.

Attack Vector

The attack vector for CVE-2021-30665 is network-based and requires user interaction. An attacker can exploit this vulnerability through the following methods:

1. Malicious Website: The attacker hosts a webpage containing specially crafted content designed to trigger the memory corruption
2. Drive-by Download: Victims are redirected to the malicious content through phishing emails, malvertising, or compromised legitimate websites
3. Embedded Content: Malicious iframes or embedded objects on otherwise legitimate websites can trigger the vulnerability

The exploitation mechanism targets the WebKit rendering engine, which is used by Safari and other applications that display web content on Apple devices. Since the vulnerability requires only that a user view malicious web content, the attack surface is significant across all affected Apple platforms.

Detection Methods for CVE-2021-30665

Indicators of Compromise

• Unexpected Safari or WebKit process crashes or abnormal behavior
• Unusual network connections to unknown external domains following web browsing
• Signs of unauthorized code execution or privilege escalation on Apple devices
• Anomalous memory usage patterns in WebKit-related processes

Detection Strategies

• Monitor system logs for WebKit process crashes or exceptions that may indicate exploitation attempts
• Implement network monitoring to detect connections to known malicious domains associated with exploit delivery
• Deploy endpoint detection solutions capable of identifying memory corruption exploitation patterns
• Review Apple device management logs for signs of unauthorized application installation or configuration changes

Monitoring Recommendations

• Enable comprehensive logging on Apple devices through MDM solutions where applicable
• Monitor for unusual process behavior, particularly parent-child process relationships involving Safari or WebKit
• Implement DNS monitoring to detect connections to suspicious domains
• Configure alerts for unexpected system configuration changes on managed Apple devices

How to Mitigate CVE-2021-30665

Immediate Actions Required

• Update all affected Apple devices to the patched versions immediately (iOS 14.5.1, iPadOS 14.5.1, iOS 12.5.3, macOS Big Sur 11.3.1, tvOS 14.6, watchOS 7.4.1)
• Prioritize patching devices used for accessing untrusted web content
• Educate users about the risks of clicking unknown links or visiting untrusted websites
• Consider temporarily restricting web browsing on unpatched critical devices

Patch Information

Apple has released security updates addressing CVE-2021-30665 across all affected platforms. The fixes improve state management within WebKit to prevent the memory corruption condition. Detailed patch information is available through the following Apple Security Advisories:

• iOS 14.5.1 and iPadOS 14.5.1 Security Update
• iOS 12.5.3 Security Update
• macOS Big Sur 11.3.1 Security Update
• tvOS 14.6 Security Update
• watchOS 7.4.1 Security Update

This vulnerability is listed in the CISA Known Exploited Vulnerabilities Catalog, requiring federal agencies to remediate according to binding operational directives.

Workarounds

• Use alternative browsers that do not rely on WebKit for rendering where possible (note: on iOS, all browsers use WebKit)
• Implement web content filtering to block access to known malicious domains
• Enable content blockers and restrict JavaScript execution on untrusted websites
• Consider network-level filtering to prevent users from accessing potentially malicious web content

Organizations should prioritize applying the official patches as the primary mitigation, as workarounds only reduce but do not eliminate the risk of exploitation.