CVE-2025-43435: Apple Safari DOS Vulnerability

CVE-2025-43435 Overview

CVE-2025-43435 is a memory handling vulnerability affecting Apple Safari and multiple Apple operating systems. Processing maliciously crafted web content can trigger an unexpected process crash on affected devices. The flaw is classified under [CWE-119], covering improper restriction of operations within the bounds of a memory buffer.

Apple addressed the issue with improved memory handling in Safari 26.1, iOS 18.7.2, iPadOS 18.7.2, iOS 26.1, iPadOS 26.1, macOS Tahoe 26.1, tvOS 26.1, visionOS 26.1, and watchOS 26.1. The vulnerability requires user interaction, since a victim must load attacker-controlled web content to trigger the crash.

Critical Impact
Remote attackers can cause a denial-of-service condition in Safari and WebKit-based content processes by serving malicious web pages to targeted users.

Affected Products

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

Discovery Timeline

2025-11-04 - CVE-2025-43435 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-43435

Vulnerability Analysis

The vulnerability resides in the memory handling logic used when processing web content within Apple's WebKit-based rendering stack. Maliciously crafted HTML, CSS, or JavaScript content can drive the renderer into an invalid memory state, resulting in an unexpected process crash. Apple's advisory notes the issue was resolved through improved memory handling, indicating a boundary or lifetime error in a buffer operation ([CWE-119]).

The impact is limited to availability. Confidentiality and integrity are not affected, and the flaw does not directly yield code execution based on the vendor description. Attack complexity is low and no privileges are required, but successful exploitation depends on a user visiting a malicious page.

Root Cause

The root cause is improper restriction of operations within a memory buffer during web content processing. Insufficient bounds checks or incorrect memory lifecycle management allow crafted inputs to place the process in an inconsistent state. Apple's fix reinforces the memory handling paths to reject or safely process the malformed data.

Attack Vector

Exploitation occurs over the network. An attacker hosts crafted web content on a malicious page or delivers it through a compromised site, advertisement, or embedded frame. When the victim loads the content in Safari or another WebKit-backed context, the renderer processes the payload and crashes. No authentication is required, but user interaction is necessary to load the page.

No public proof-of-concept, exploit code, or CISA KEV listing exists for this issue at the time of publication. The EPSS probability is 0.685%.

Detection Methods for CVE-2025-43435

Indicators of Compromise

Repeated unexpected termination of Safari or WebKit-based content processes such as com.apple.WebKit.WebContent on macOS and iOS devices.
CrashReporter logs referencing WebKit or JavaScriptCore memory faults following visits to untrusted URLs.
Endpoint telemetry showing browser processes spawning crash-reporting helpers immediately after network activity to suspicious domains.

Detection Strategies

Monitor macOS unified logs and iOS crash reports for recurring WebKit content process terminations tied to specific origins.
Correlate web proxy or DNS logs with browser crash events to identify sites that reliably trigger renderer failures.
Track Safari version inventory across the fleet to identify endpoints still running builds prior to Safari 26.1.

Monitoring Recommendations

Ingest macOS crash reports and browser telemetry into a centralized analytics platform for anomaly detection.
Alert when the rate of WebKit content process crashes on a device exceeds a normal baseline within a short window.
Review threat intelligence feeds for URLs and campaigns delivering crash-inducing WebKit payloads.

How to Mitigate CVE-2025-43435

Immediate Actions Required

Update Safari to version 26.1 on all supported macOS releases where the standalone Safari update applies.
Upgrade iPhone and iPad devices to iOS 18.7.2 or iOS 26.1 and iPadOS 18.7.2 or iPadOS 26.1.
Apply macOS Tahoe 26.1, tvOS 26.1, visionOS 26.1, and watchOS 26.1 to all remaining Apple endpoints.
Enforce update compliance through MDM policies and block enrollment for devices running vulnerable builds.

Patch Information

Apple released fixes across the affected platforms as documented in the vendor advisories: Apple Support Article #125632, Apple Support Article #125633, Apple Support Article #125634, Apple Support Article #125637, Apple Support Article #125638, Apple Support Article #125639, and Apple Support Article #125640.

Workarounds

Restrict browsing to trusted sites through web content filtering or secure web gateway policies until patches are deployed.
Enable Lockdown Mode on high-risk Apple devices to reduce the WebKit attack surface.
Disable JavaScript for untrusted origins in enterprise-managed browser profiles where feasible.

bash

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

# Query iOS/iPadOS build compliance via MDM (example: Jamf Pro API)
curl -s -u "$JAMF_USER:$JAMF_PASS" \
  "https://$JAMF_HOST/JSSResource/mobiledevices/match/*" \
  | grep -E "os_version|serial_number"