CVE-2026-39872: Apple Safari DOS Vulnerability

CVE-2026-39872 Overview

CVE-2026-39872 is a memory handling vulnerability affecting Apple Safari, iOS, iPadOS, and macOS. Processing maliciously crafted web content can trigger an unexpected process crash, resulting in denial of service. The flaw is categorized under [CWE-119] (improper restriction of operations within the bounds of a memory buffer). Apple addressed the issue with improved memory handling in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. The vulnerability requires user interaction, typically visiting a malicious webpage, and does not require authentication.

Critical Impact
Attackers can crash the browser or system processes on unpatched Apple devices by delivering crafted web content, disrupting availability without authentication.

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-2026-39872 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2026-39872

Vulnerability Analysis

CVE-2026-39872 resides in Apple's WebKit-based web content processing stack. When Safari or a WebKit-embedded component parses specifically crafted web content, improper memory handling triggers an unexpected process crash. Apple's advisory classifies the fix as an improvement to memory handling, consistent with [CWE-119] memory buffer boundary issues.

The defect affects availability only. Confidentiality and integrity are not impacted based on the published CVSS vector. Exploitation requires a victim to load attacker-controlled web content, which is a low-friction condition for browsers and any application embedding WebKit views.

No public proof-of-concept exploit is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS probability remains low at 0.194%, indicating limited likelihood of exploitation activity in the near term.

Root Cause

The root cause is improper memory handling during processing of maliciously crafted web content within Apple's WebKit rendering engine. Apple has not disclosed the specific function or code path, but the [CWE-119] classification indicates memory operations that exceed intended buffer boundaries. Apple resolved the issue by introducing stricter memory handling checks in the affected code paths.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts crafted web content on a controlled site or injects it into a compromised page. When a victim visits the page in a vulnerable Safari version, or opens the content in any application using an affected WebKit component, the renderer process crashes. Phishing campaigns, malvertising, and drive-by delivery are plausible delivery channels for such content.

No verified exploit code is publicly available. See the Apple Support Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for vendor guidance.

Detection Methods for CVE-2026-39872

Indicators of Compromise

Repeated or unexplained crashes of Safari, WebContent, or com.apple.WebKit.WebContent processes on macOS, iOS, or iPadOS endpoints.
Crash reports referencing WebKit memory faults following navigation to untrusted URLs.
Endpoint telemetry showing Safari versions prior to 26.5.2 or operating system builds prior to iOS/iPadOS/macOS Tahoe 26.5.2.

Detection Strategies

Inventory Apple endpoints and identify devices running Safari, iOS, iPadOS, or macOS versions below 26.5.2.
Correlate browser process crash events with recent web navigation history to identify potentially malicious content sources.
Monitor threat intelligence feeds for domains hosting WebKit-targeted crafted content associated with this CVE.

Monitoring Recommendations

Ingest macOS unified logs and iOS crash telemetry into a centralized logging platform to detect WebKit process termination patterns.
Track Safari and OS version compliance across managed devices using MDM reporting.
Alert on high-frequency renderer crashes originating from a single web origin, which can indicate targeting or automated probing.

How to Mitigate CVE-2026-39872

Immediate Actions Required

Update Safari to version 26.5.2 on all managed macOS endpoints.
Upgrade iOS and iPadOS devices to version 26.5.2 through MDM or user-initiated updates.
Upgrade macOS Tahoe systems to 26.5.2 to receive the WebKit memory handling fix.
Prioritize patching for devices used to access untrusted web content or high-risk user populations.

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 Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for release notes and installation guidance.

Workarounds

Restrict browsing to trusted sites and enforce web content filtering at the network perimeter until patches are deployed.
Disable JavaScript in Safari for high-risk users where feasible to reduce the attack surface for crafted web content.
Use alternative browsers on unpatched macOS systems for accessing untrusted content, noting that WebKit-embedded apps remain affected.

bash

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

# Check macOS version
sw_vers -productVersion

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