CVE-2024-40817: Apple Safari XSS Vulnerability

CVE-2024-40817 Overview

CVE-2024-40817 is a UI spoofing vulnerability affecting Apple Safari and macOS systems. The issue stems from improper UI handling that allows attackers to manipulate the user interface when victims visit websites containing malicious framed content. This vulnerability was addressed by Apple through improved UI handling mechanisms in the affected products.

Critical Impact

Visiting a website that frames malicious content may lead to UI spoofing, potentially enabling phishing attacks, credential theft, or user deception through fake interface elements.

Affected Products

• Apple Safari versions prior to 17.6
• Apple macOS Sonoma versions prior to 14.6
• Apple macOS Monterey versions prior to 12.7.6
• Apple macOS Ventura versions prior to 13.6.8

Discovery Timeline

• July 29, 2024 - CVE-2024-40817 published to NVD
• November 4, 2025 - Last updated in NVD database

Technical Details for CVE-2024-40817

Vulnerability Analysis

This vulnerability is classified under CWE-1021 (Improper Restriction of Rendered UI Layers or Frames), which relates to improper handling of UI elements when rendering framed content. The flaw allows malicious actors to craft websites with specially designed framed content that can manipulate or spoof legitimate UI elements displayed to the user.

The vulnerability requires user interaction, as victims must visit a malicious website for the attack to succeed. However, once a user navigates to such a site, the attacker can overlay or modify UI elements to deceive the user into taking unintended actions, such as entering credentials into fake login forms or clicking on disguised elements.

Root Cause

The root cause of this vulnerability lies in Safari's improper handling of UI rendering when processing framed content from untrusted sources. The browser failed to properly isolate or restrict how framed content could interact with or influence the displayed user interface, allowing malicious frames to create convincing spoofed UI elements that appear legitimate to the end user.

Attack Vector

The attack leverages a network-based vector where attackers host malicious websites containing specially crafted framed content. When a victim visits such a site, the malicious frames can manipulate the browser's UI rendering to display spoofed elements.

The exploitation flow typically involves:

1. Attacker creates a malicious website with carefully constructed iframe or frame elements
2. The framed content is designed to overlay or mimic legitimate browser UI components
3. Victim visits the malicious website through normal browsing or via a phishing link
4. The spoofed UI elements deceive the user into believing they are interacting with legitimate interface components
5. User may unknowingly submit credentials, approve actions, or interact with attacker-controlled elements

This type of attack is particularly effective for phishing campaigns and social engineering attacks where visual deception is key to compromising user trust.

Detection Methods for CVE-2024-40817

Indicators of Compromise

• Unusual iframe or frame element behavior in web page rendering
• User reports of unexpected UI elements or overlays appearing during browsing sessions
• Phishing attempts that leverage pixel-perfect browser UI spoofing
• Websites with complex nested framing structures designed to obscure content origin

Detection Strategies

• Monitor for browser behavior anomalies when rendering framed content
• Implement content security policies that restrict framing from untrusted sources
• Deploy endpoint detection tools capable of identifying UI manipulation attempts
• Analyze web traffic for suspicious framing patterns targeting Safari users

Monitoring Recommendations

• Enable Safari's built-in security features and keep them updated
• Monitor endpoint logs for unusual browser process behavior
• Track user-reported phishing attempts that may exploit this vulnerability
• Review web application logs for attempts to load content in manipulative frame structures

How to Mitigate CVE-2024-40817

Immediate Actions Required

• Update Safari to version 17.6 or later immediately
• Update macOS Sonoma to version 14.6 or later
• Update macOS Monterey to version 12.7.6 or later
• Update macOS Ventura to version 13.6.8 or later
• Enable automatic updates to ensure timely security patch deployment

Patch Information

Apple has released security updates addressing this vulnerability across multiple products. Detailed patch information is available in the following security advisories:

• Apple Security Update HT214118 - Safari 17.6
• Apple Security Update HT214119 - macOS Sonoma 14.6
• Apple Security Update HT214120 - macOS Ventura 13.6.8
• Apple Security Update HT214121 - macOS Monterey 12.7.6

Additional technical details were disclosed via the Full Disclosure Mailing List.

Workarounds

• Exercise caution when visiting unfamiliar websites, especially those with complex framing structures
• Use browser extensions that block or restrict iframe loading from untrusted domains
• Implement organizational policies restricting access to known malicious domains
• Consider enabling strict content security policies on internal web applications to prevent framing attacks
• Educate users about UI spoofing risks and phishing identification techniques

# Check Safari version on macOS
/Applications/Safari.app/Contents/MacOS/Safari --version

# Check macOS version
sw_vers -productVersion

# Enable automatic updates via command line
sudo softwareupdate --schedule on