CVE-2026-43734: Apple Safari Use-After-Free Vulnerability

CVE-2026-43734 Overview

CVE-2026-43734 is a use-after-free vulnerability [CWE-416] affecting Apple Safari, iOS, iPadOS, and macOS Tahoe. The flaw resides in web content processing and can be triggered when a user visits maliciously crafted web content. Successful exploitation leads to an unexpected process crash, causing a denial-of-service condition on the affected device. 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 vulnerability requires user interaction, as the victim must load attacker-controlled web content in a vulnerable browser or embedded WebKit component.

Critical Impact
Processing maliciously crafted web content triggers a use-after-free condition, resulting in an unexpected process crash and denial of service on Apple devices.

Affected Products

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

Discovery Timeline

2026-06-29 - CVE-2026-43734 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2026-43734

Vulnerability Analysis

The vulnerability is a use-after-free memory corruption issue in Apple's web content processing stack. A use-after-free occurs when a program continues to reference memory after it has been freed, allowing the freed region to be accessed or manipulated. In browser engines, such flaws commonly arise from object lifetime mismanagement between the JavaScript engine, the DOM, and rendering layers. An attacker who hosts crafted HTML, CSS, or JavaScript can force the WebKit process to dereference a stale pointer. The result observed for this issue is an unexpected process crash rather than confirmed code execution.

Root Cause

Apple's advisory attributes the issue to improper memory management within the affected component. The fix is described as improved memory management, indicating that object lifetime and reference tracking were adjusted to prevent access to freed memory. The underlying weakness class is CWE-416 (Use After Free).

Attack Vector

Exploitation is network-based and requires user interaction. A victim must load a page or content controlled by the attacker in Safari or in an application that embeds WebKit. No authentication or elevated privileges are required by the attacker. The observed impact is limited to availability, with the affected process terminating unexpectedly.

No public proof-of-concept code has been released. Refer to the Apple Support Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for vendor-supplied technical details.

Detection Methods for CVE-2026-43734

Indicators of Compromise

Repeated unexpected crashes of Safari, WebContent, or WebKit-hosted processes on macOS, iOS, or iPadOS endpoints.
Crash reports referencing WebKit frames generated shortly after visiting untrusted or newly registered domains.
Outbound connections from browser processes to low-reputation URLs immediately preceding a crash event.

Detection Strategies

Collect and centralize macOS DiagnosticReports and iOS crash logs to identify recurring WebKit crashes across a fleet.
Correlate browser process termination events with recently visited URLs to isolate suspicious content sources.
Monitor endpoint telemetry for repeated WebContent process restarts on hosts running Safari versions prior to 26.5.2.

Monitoring Recommendations

Track Safari and WebKit version inventory across managed Apple endpoints to identify unpatched systems.
Alert on anomalous clusters of browser crashes across multiple users visiting the same domain.
Enrich web proxy logs with URL reputation data to flag traffic that precedes browser instability.

How to Mitigate CVE-2026-43734

Immediate Actions Required

Update Safari to version 26.5.2 on all managed macOS systems.
Upgrade iOS and iPadOS devices to version 26.5.2 through MDM-enforced update policies.
Update macOS Tahoe hosts to 26.5.2 to patch the embedded WebKit component.
Restrict browsing to trusted sites on any device that cannot be immediately updated.

Patch Information

Apple has released fixes in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. The patch introduces improved memory management to eliminate the use-after-free condition. Administrators should consult the vendor guidance in Apple Support Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for full version and build details.

Workarounds

Enforce update compliance through Mobile Device Management (MDM) profiles to ensure timely patch adoption.
Use web content filtering or DNS filtering to block access to untrusted domains until patches are deployed.
Advise users to avoid opening untrusted links in Safari or WebKit-based apps on unpatched devices.

bash

# Verify installed Safari version on macOS
mdls -name kMDItemVersion /Applications/Safari.app

# Trigger a software update check on macOS
sudo softwareupdate --list
sudo softwareupdate --install --all --restart