CVE-2025-43434: Apple Safari Use-After-Free Vulnerability

CVE-2025-43434 Overview

CVE-2025-43434 is a use-after-free memory corruption vulnerability [CWE-416] affecting Apple Safari and multiple Apple operating systems. Processing maliciously crafted web content can trigger an unexpected Safari crash, resulting in a denial-of-service condition. The flaw resides in the browser's memory management routines, where a freed object is referenced during content parsing or rendering. Apple resolved the issue with improved memory management in Safari 26.1, iOS 18.7.2, iPadOS 18.7.2, iOS 26.1, iPadOS 26.1, macOS Tahoe 26.1, visionOS 26.1, and watchOS 26.1. The vulnerability requires user interaction, typically visiting an attacker-controlled webpage, and does not require authentication.

Critical Impact
Remote attackers can crash Safari by delivering crafted web content, disrupting browsing sessions across Apple's ecosystem including iPhone, iPad, Mac, Apple Watch, and Apple Vision Pro.

Affected Products

Apple Safari (versions prior to 26.1)
Apple iOS and iPadOS (versions prior to 18.7.2 and 26.1)
Apple macOS Tahoe (versions prior to 26.1), visionOS (prior to 26.1), and watchOS (prior to 26.1)

Discovery Timeline

2025-11-04 - CVE-2025-43434 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-43434

Vulnerability Analysis

The vulnerability is a use-after-free (UAF) condition classified under [CWE-416]. UAF flaws occur when a program continues to use a pointer after the memory it references has been freed. Attackers can leverage this dangling pointer to read stale data, trigger crashes, or in some cases influence control flow.

In this case, Apple documents the impact as an unexpected Safari crash triggered by processing maliciously crafted web content. The confidentiality and integrity impacts are rated as none, while availability is rated low, consistent with a browser-tab crash rather than sandbox escape or code execution.

Because Safari and WebKit are shared across the Apple platform, the same underlying WebKit component is affected on iOS, iPadOS, macOS, visionOS, and watchOS. The EPSS probability is approximately 1.18%, placing it in the 64th percentile for likelihood of exploitation activity.

Root Cause

Apple's advisory states the issue was addressed with improved memory management. This language indicates an object lifetime bug in the rendering or JavaScript engine, where a reference persists after the associated memory has been released. Interaction between garbage-collected script objects and reference-counted native objects is a common source of such flaws in browser engines.

Attack Vector

An attacker hosts crafted HTML, CSS, or JavaScript content on a webpage. When a victim visits the page in an unpatched Safari build, the browser dereferences a freed object and crashes. Delivery vectors include phishing links, malicious advertising, and compromised legitimate sites. No credentials are required, and exploitation happens over the network.

No public proof-of-concept, exploit code, or in-the-wild exploitation has been reported for CVE-2025-43434. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Detection Methods for CVE-2025-43434

Indicators of Compromise

Repeated or unexplained Safari or WebKit process crashes recorded in system diagnostic logs (~/Library/Logs/DiagnosticReports/ on macOS)
Crash reports referencing WebKit rendering, JavaScriptCore, or WebContent process termination shortly after visiting a specific URL
Outbound network connections from Safari to newly registered or low-reputation domains preceding a crash event

Detection Strategies

Inventory Apple endpoints and compare installed Safari, iOS, iPadOS, macOS, visionOS, and watchOS versions against the fixed releases listed in Apple's advisories
Monitor endpoint telemetry for abnormal WebContent process termination patterns and correlate with the URLs loaded immediately before termination
Use web filtering to flag access to unknown or newly observed domains hosting complex JavaScript payloads targeting WebKit

Monitoring Recommendations

Collect and centralize macOS ReportCrash and iOS crash diagnostics for review by security operations
Alert on clusters of Safari crashes across multiple users reaching the same web resource
Track browser and OS patch compliance on managed Apple devices through MDM reporting

How to Mitigate CVE-2025-43434

Immediate Actions Required

Update Safari to version 26.1 on supported macOS releases
Upgrade iOS and iPadOS devices to 18.7.2 or 26.1, and update macOS Tahoe, visionOS, and watchOS to 26.1
Prioritize patching for users who handle sensitive data or browse untrusted content, and enforce updates through Mobile Device Management (MDM)

Patch Information

Apple released fixes across its product line. Refer to the vendor advisories for exact build numbers and download instructions: Apple Support Article #125632, Apple Support Article #125633, Apple Support Article #125634, Apple Support Article #125638, Apple Support Article #125639, and Apple Support Article #125640.

Workarounds

Restrict Safari usage to trusted sites until patches are applied, and consider a temporary alternative browser for high-risk browsing
Enable Lockdown Mode on iOS, iPadOS, and macOS for high-value users, which reduces WebKit's attack surface
Deploy content filtering and DNS-layer protections to block known malicious domains that host WebKit exploitation payloads

bash

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

# Check macOS build version
sw_vers

# Trigger managed software updates via MDM (example: Jamf)
sudo jamf policy -event installAppleUpdates