CVE-2025-43427: Apple Safari DOS Vulnerability

CVE-2025-43427 Overview

CVE-2025-43427 is an input validation weakness [CWE-20] affecting Apple's web content processing across Safari and multiple operating systems. Processing maliciously crafted web content may lead to an unexpected process crash, resulting in a denial-of-service condition for the affected process. Apple addressed the flaw through improved state management. The vulnerability requires user interaction, such as visiting an attacker-controlled webpage, and does not require any privileges. Apple fixed the issue in Safari 26.1, iOS 26.1, iPadOS 26.1, macOS Tahoe 26.1, tvOS 26.1, and visionOS 26.1.

Critical Impact
A remote attacker can trigger an unexpected process crash by luring a user to malicious web content, disrupting browser availability across Apple's ecosystem.

Affected Products

Apple Safari (prior to 26.1)
Apple iOS and iPadOS (prior to 26.1)
Apple macOS Tahoe (prior to 26.1)
Apple tvOS and visionOS (prior to 26.1)

Discovery Timeline

2025-11-04 - CVE-2025-43427 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-43427

Vulnerability Analysis

The vulnerability resides in Apple's web content processing pipeline, shared across Safari and the WebKit-based rendering used on iOS, iPadOS, macOS, tvOS, and visionOS. Apple's advisory attributes the fix to improved state management, indicating that the underlying process reached an inconsistent internal state when handling specific crafted web content. That state confusion triggers an unexpected crash of the web content process.

The issue is classified under [CWE-20] Improper Input Validation. The impact is limited to availability, with no confidentiality or integrity consequences reported by Apple. Exploitation requires the target to load attacker-controlled content, which is achievable through phishing links, malvertising, or compromised sites.

Root Cause

The root cause is improper state management during the parsing or rendering of untrusted web content. When specific input sequences are processed, the affected component transitions into an unexpected state that is not correctly handled by downstream logic. This leads to an abnormal termination of the process rather than a controlled error path.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts crafted HTML, JavaScript, or related web content on a page under their control. When a user visits the page in a vulnerable version of Safari or another WebKit consumer on the listed operating systems, the content triggers the state inconsistency and crashes the web content process. No authentication or elevated privileges are required.

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

Detection Methods for CVE-2025-43427

Indicators of Compromise

Recurring or unexplained crashes of the Safari web content process or com.apple.WebKit.WebContent on macOS and iOS devices.
Crash reports referencing WebKit rendering components generated shortly after visiting unfamiliar URLs.
Outbound connections from Apple endpoints to newly registered or low-reputation domains preceding browser crashes.

Detection Strategies

Monitor endpoint telemetry for abnormal termination events of WebKit-hosted processes on macOS and iOS-family devices.
Correlate browser process crashes with URL history and web proxy logs to identify potentially malicious pages.
Track software inventory to flag endpoints still running Safari, iOS, iPadOS, macOS, tvOS, or visionOS versions below 26.1.

Monitoring Recommendations

Ingest macOS unified logs and crash reports into a central analytics platform to identify clusters of WebKit crashes across the fleet.
Baseline normal Safari process behavior and alert on anomalous crash frequency for individual users.
Review web gateway logs for repeated visits to the same URL immediately before crash events.

How to Mitigate CVE-2025-43427

Immediate Actions Required

Update all Apple devices to Safari 26.1, iOS 26.1, iPadOS 26.1, macOS Tahoe 26.1, tvOS 26.1, or visionOS 26.1 as applicable.
Prioritize patching for high-risk users such as executives, developers, and those handling sensitive data on Apple endpoints.
Verify managed device compliance through MDM reporting after deploying the updates.

Patch Information

Apple released fixes in Safari 26.1, iOS 26.1 and iPadOS 26.1, macOS Tahoe 26.1, tvOS 26.1, and visionOS 26.1. Refer to Apple's advisories for full details: Apple Support Advisory #125632, Apple Support Advisory #125634, Apple Support Advisory #125637, Apple Support Advisory #125638, and Apple Support Advisory #125640.

Workarounds

Restrict browsing to trusted sites via corporate web filtering until patches are deployed.
Advise users to avoid clicking untrusted links in email, messaging apps, and social media.
Where feasible, use alternate managed browsers on macOS while updates propagate to unmanaged devices.

bash

# Verify Safari and macOS versions across managed endpoints
sw_vers -productVersion
defaults read /Applications/Safari.app/Contents/Info.plist CFBundleShortVersionString

# Trigger MDM-managed software update on macOS
sudo softwareupdate --install --all --restart