CVE-2026-20644: Apple Safari DOS Vulnerability

CVE-2026-20644 Overview

CVE-2026-20644 is a memory handling vulnerability affecting Apple's Safari browser and WebKit engine across multiple Apple platforms including macOS, iOS, iPadOS, and visionOS. The vulnerability exists due to improper memory handling when processing web content, which can be exploited by an attacker to cause an unexpected process crash. This denial of service condition can be triggered when a victim visits a maliciously crafted webpage.

Critical Impact

Processing maliciously crafted web content may lead to an unexpected process crash, enabling denial of service attacks against Apple device users through Safari and WebKit-based applications.

Affected Products

• Apple Safari versions prior to 26.3
• Apple macOS Tahoe versions prior to 26.3
• Apple iOS versions prior to 18.7.5 and 26.3
• Apple iPadOS versions prior to 18.7.5 and 26.3
• Apple visionOS versions prior to 26.3

Discovery Timeline

• 2026-02-11 - CVE-2026-20644 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2026-20644

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in WebKit's memory handling routines when processing web content. When specially crafted web content is processed, the browser fails to properly manage memory boundaries, leading to a buffer access that can cause the affected process to crash unexpectedly.

The attack requires network access and user interaction—specifically, the victim must visit a malicious webpage or view attacker-controlled web content. While this vulnerability does not appear to allow code execution or information disclosure, it provides a reliable mechanism for crashing Safari or WebKit-based applications, which could be leveraged in targeted denial of service attacks or as part of a multi-stage attack chain.

Root Cause

The root cause stems from improper restriction of operations within memory buffer boundaries (CWE-119). During web content processing, WebKit fails to properly validate or handle memory operations, allowing malformed input to trigger memory access violations. Apple addressed this by implementing improved memory handling routines that properly validate and constrain memory operations during content processing.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker can exploit this vulnerability by:

1. Hosting malicious web content on an attacker-controlled website
2. Luring victims to visit the malicious page through phishing, social engineering, or compromised legitimate websites
3. Delivering the malicious content through WebKit-based applications that render web content
4. Embedding malicious content in advertisements or third-party widgets

The vulnerability triggers during the parsing or rendering phase of web content processing, causing the Safari process or the embedding application to crash unexpectedly. This can disrupt user workflows, cause data loss in unsaved web applications, and potentially be used to mask other malicious activities.

Detection Methods for CVE-2026-20644

Indicators of Compromise

• Frequent unexpected Safari or WebKit process crashes when browsing specific websites
• Crash reports indicating memory access violations in WebKit-related processes
• Users reporting repeated browser crashes when viewing particular web content
• System logs showing com.apple.WebKit.WebContent process terminations

Detection Strategies

• Monitor for abnormal crash patterns in Safari and WebKit processes across endpoints
• Implement web filtering to block known malicious domains hosting exploit content
• Deploy endpoint detection rules that alert on repeated WebKit process crashes
• Analyze crash logs for patterns indicative of memory corruption exploitation attempts

Monitoring Recommendations

• Enable crash reporting and centralize Safari/WebKit crash logs for analysis
• Monitor network traffic for connections to suspicious domains prior to browser crashes
• Implement SentinelOne Singularity endpoint protection to detect exploitation attempts
• Track software versions across the fleet to identify unpatched systems

How to Mitigate CVE-2026-20644

Immediate Actions Required

• Update Safari to version 26.3 or later immediately
• Update macOS Tahoe to version 26.3 or later
• Update iOS and iPadOS to version 18.7.5 or 26.3 or later
• Update visionOS to version 26.3 or later
• Enable automatic updates on all Apple devices to receive security patches promptly

Patch Information

Apple has released security updates to address this vulnerability across all affected platforms. The fix involves improved memory handling to prevent the crash condition. Patches are available through the following Apple Security Advisories:

• Apple Security Advisory 126346
• Apple Security Advisory 126347
• Apple Security Advisory 126348
• Apple Security Advisory 126353
• Apple Security Advisory 126354

Organizations should prioritize patching Safari and associated operating systems to the fixed versions: Safari 26.3, macOS Tahoe 26.3, iOS 18.7.5/26.3, iPadOS 18.7.5/26.3, and visionOS 26.3.

Workarounds

• Use alternative browsers that do not rely on WebKit until patches can be applied
• Implement web content filtering to restrict access to untrusted websites
• Enable content blockers or ad blockers to reduce exposure to malicious web content
• Disable JavaScript on untrusted sites as a temporary risk reduction measure
• Use network-level protections to filter potentially malicious web traffic

# Check current Safari version on macOS
/usr/bin/defaults read /Applications/Safari.app/Contents/Info CFBundleShortVersionString

# Check for available software updates on macOS
softwareupdate --list

# Install all available updates
softwareupdate --install --all