CVE-2026-43727: Apple Safari Use-After-Free Vulnerability

CVE-2026-43727 Overview

CVE-2026-43727 is a use-after-free vulnerability [CWE-416] affecting Apple Safari and multiple Apple operating systems. Processing maliciously crafted web content may lead to an unexpected Safari crash. Apple addressed the issue with improved memory management in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. The flaw requires user interaction, such as visiting an attacker-controlled webpage, to trigger the memory corruption condition.

Critical Impact
Remote attackers can trigger an unexpected Safari crash by delivering maliciously crafted web content, resulting in a denial-of-service condition on affected Apple devices.

Affected Products

Apple Safari (versions prior to 26.5.2)
Apple iOS and iPadOS (versions prior to 26.5.2)
Apple macOS Tahoe (versions prior to 26.5.2)

Discovery Timeline

2026-06-29 - CVE-2026-43727 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2026-43727

Vulnerability Analysis

The vulnerability is a use-after-free condition [CWE-416] in Apple Safari's web content processing pipeline. A use-after-free occurs when a program continues to reference memory after it has been freed, allowing an attacker to influence program behavior through the reuse of that memory region. In this case, processing maliciously crafted web content triggers the condition and leads to an unexpected Safari crash.

The attack requires network delivery and user interaction. A victim must load attacker-controlled web content in a vulnerable Safari version to trigger the flaw. The documented impact is availability loss through browser crash, with no confirmed confidentiality or integrity impact according to the CVSS vector.

Root Cause

The root cause is improper lifetime management of an object in Safari's memory allocator during web content processing. Apple's advisory states the issue was addressed through improved memory management, indicating that the affected code path failed to invalidate or update a dangling reference after the underlying object was released.

Attack Vector

Exploitation is remote and requires user interaction. An attacker hosts crafted HTML, JavaScript, or associated web content on a controlled or compromised site. When a user navigates to that content in a vulnerable Safari build, the browser dereferences freed memory and crashes. Delivery vehicles include phishing links, malvertising, and cross-site inclusion of hostile resources.

No public proof-of-concept or in-the-wild exploitation has been reported. The CVE is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-43727

Indicators of Compromise

Repeated or unexpected Safari process crashes (com.apple.Safari, WebKit, com.apple.WebKit.WebContent) correlated with web browsing activity.
Crash reports in ~/Library/Logs/DiagnosticReports/ referencing WebKit content processes with memory access violations.
Outbound connections from endpoints to newly observed or low-reputation domains immediately preceding browser crashes.

Detection Strategies

Monitor endpoint telemetry for abnormal termination of Safari and WebKit content processes on macOS, iOS, and iPadOS devices.
Correlate browser crash events with recent URL navigation history to identify suspect web content.
Track Safari and OS version inventory across the fleet to identify devices still running versions prior to 26.5.2.

Monitoring Recommendations

Ingest macOS unified logs and diagnostic reports into a centralized logging platform to detect WebKit crash patterns at scale.
Alert on clusters of Safari crashes affecting multiple endpoints, which may indicate a shared malicious URL.
Review web proxy logs for user navigation to domains flagged by threat intelligence prior to crash events.

How to Mitigate CVE-2026-43727

Immediate Actions Required

Update Safari to version 26.5.2 on macOS endpoints where the browser is installed independently.
Upgrade iOS and iPadOS devices to version 26.5.2 through Software Update or mobile device management (MDM).
Upgrade macOS Tahoe endpoints to version 26.5.2 to receive the bundled Safari and WebKit fixes.
Verify patch deployment across managed and BYOD Apple devices using inventory reporting.

Patch Information

Apple released fixes in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. Refer to Apple Support Document #127594, Apple Support Document #127595, and Apple Support Document #127685 for release details and applicability by product.

Workarounds

Restrict browsing to trusted sites and block access to untrusted domains through web filtering until patches are applied.
Use an alternative browser on macOS for high-risk browsing tasks until Safari is updated.
Enforce mandatory OS and browser updates through MDM policies to reduce exposure windows.

bash

# Verify Safari version on macOS
defaults read /Applications/Safari.app/Contents/Info.plist CFBundleShortVersionString

# Check macOS version
sw_vers -productVersion