CVE-2024-27856: Apple Safari RCE Vulnerability Explained

CVE-2024-27856 Overview

CVE-2024-27856 is a code injection vulnerability affecting multiple Apple operating systems and Safari browser. The vulnerability stems from insufficient input validation during file processing, which can lead to unexpected application termination or arbitrary code execution. An attacker could exploit this flaw by crafting a malicious file that, when processed by a vulnerable application, triggers the security bypass and enables code injection.

Critical Impact

Processing a maliciously crafted file may lead to unexpected app termination or arbitrary code execution across iOS, iPadOS, macOS, watchOS, tvOS, visionOS, and Safari.

Affected Products

• Apple Safari (versions prior to 17.5)
• Apple macOS Sonoma (versions prior to 14.5)
• Apple iOS and iPadOS (versions prior to 17.5 and 16.7.8)
• Apple watchOS (versions prior to 10.5)
• Apple tvOS (versions prior to 17.5)
• Apple visionOS (versions prior to 1.2)

Discovery Timeline

• January 15, 2025 - CVE-2024-27856 published to NVD
• March 14, 2025 - Last updated in NVD database

Technical Details for CVE-2024-27856

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code, also known as Code Injection). The flaw exists in how Apple's file processing mechanisms handle certain input data. When a specially crafted file is processed, the insufficient validation allows an attacker to inject and execute arbitrary code within the context of the affected application.

The vulnerability requires local access and user interaction to exploit, meaning an attacker must convince a user to open or process a malicious file. Once triggered, the vulnerability can lead to complete compromise of confidentiality, integrity, and availability of the affected system. This presents significant risk particularly in scenarios involving document handling, media file processing, or web content rendering in Safari.

Root Cause

The root cause of CVE-2024-27856 lies in improper input validation checks during file processing operations. Apple's advisory indicates the issue was addressed with "improved checks," suggesting that the vulnerable code path did not adequately sanitize or validate file content before processing. This lack of proper bounds checking or input sanitization allows malformed file data to be interpreted as executable code or commands.

Attack Vector

The attack vector for this vulnerability is local, requiring user interaction. An attacker would typically:

1. Craft a malicious file designed to exploit the vulnerable file processing logic
2. Deliver the file to the target through various means (email attachment, download link, AirDrop, etc.)
3. Convince the user to open or process the file
4. Upon processing, the vulnerability triggers code injection, allowing arbitrary code execution with the privileges of the current user

The exploitation does not require any special privileges, making it accessible to a wide range of potential attackers. The impact affects confidentiality, integrity, and availability equally, meaning successful exploitation could result in data theft, system modification, or denial of service.

Detection Methods for CVE-2024-27856

Indicators of Compromise

• Unexpected application crashes or terminations when processing files
• Anomalous process spawning from Safari, Preview, or other file-handling applications
• Unusual system calls or network connections initiated by document processing applications
• Presence of suspicious files with unexpected content or malformed headers

Detection Strategies

• Monitor for unusual process behavior following file open operations across Apple devices
• Implement endpoint detection rules to identify code execution attempts from file processing contexts
• Deploy behavioral analysis to detect anomalous activity patterns in Safari and system applications
• Review system logs for crash reports indicating file processing failures

Monitoring Recommendations

• Enable enhanced logging on macOS and iOS devices for file processing operations
• Monitor for unexpected child processes spawned by Safari or document handling applications
• Implement network monitoring to detect potential data exfiltration following document access
• Use SentinelOne's behavioral AI to detect anomalous code execution patterns indicative of exploitation

How to Mitigate CVE-2024-27856

Immediate Actions Required

• Update all Apple devices to the patched versions immediately
• Exercise caution when opening files from untrusted or unknown sources
• Enable automatic updates on all Apple devices to ensure timely security patch deployment
• Review and restrict file handling permissions where possible

Patch Information

Apple has released security updates addressing this vulnerability across all affected platforms. Organizations and users should apply the following updates:

• macOS Sonoma 14.5 - Apple Security Advisory 120896
• iOS 17.5 and iPadOS 17.5 - Apple Security Advisory 120898
• iOS 16.7.8 and iPadOS 16.7.8 - Apple Security Advisory 120905
• Safari 17.5 - Apple Security Advisory 120902
• watchOS 10.5 - Apple Security Advisory 120901
• tvOS 17.5 - Apple Security Advisory 120903
• visionOS 1.2 - Apple Security Advisory 120906

Workarounds

• Avoid opening files from untrusted sources until patches can be applied
• Use mobile device management (MDM) solutions to restrict file handling capabilities
• Implement network-level filtering to block suspicious file downloads
• Consider disabling automatic file preview features where possible until updates are applied

# Check current macOS version
sw_vers -productVersion

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

# Enable automatic updates on macOS
sudo softwareupdate --schedule on