CVE-2024-43091: Google Android RCE Vulnerability

CVE-2024-43091 Overview

CVE-2024-43091 is a critical integer overflow vulnerability discovered in the filterMask function within SkEmbossMaskFilter.cpp, a component of the Skia graphics library used in Android. The vulnerability allows an attacker to trigger an out-of-bounds write condition through integer overflow, potentially enabling remote code execution without requiring any user interaction or additional execution privileges.

Critical Impact

This vulnerability enables remote code execution on affected Android devices without user interaction. The flaw in the Skia graphics engine affects Android versions 12.0 through 15.0, exposing a massive number of devices to potential compromise.

Affected Products

• Google Android 12.0
• Google Android 12.1
• Google Android 13.0
• Google Android 14.0
• Google Android 15.0

Discovery Timeline

• November 13, 2024 - CVE-2024-43091 published to NVD
• December 17, 2024 - Last updated in NVD database

Technical Details for CVE-2024-43091

Vulnerability Analysis

The vulnerability exists in the Skia graphics library's emboss mask filter implementation. Skia is a core graphics engine used by Android for rendering 2D graphics, text, and images. The filterMask function in SkEmbossMaskFilter.cpp contains an integer overflow flaw that occurs during mask filtering operations.

When processing specially crafted graphics data, the integer overflow bypasses bounds checking mechanisms, allowing an attacker to write data beyond the allocated buffer boundaries. This out-of-bounds write can corrupt adjacent memory structures, potentially allowing arbitrary code execution within the context of the graphics rendering process.

The vulnerability is particularly dangerous because it requires no user interaction and can be triggered remotely through malicious content that invokes the vulnerable graphics rendering path.

Root Cause

The root cause is an integer overflow vulnerability (CWE-190) in the filterMask function of SkEmbossMaskFilter.cpp. When calculating buffer sizes or offsets during mask filtering operations, integer multiplication or addition operations can overflow, resulting in a smaller-than-expected allocation or incorrect bounds calculations. This allows subsequent write operations to exceed the actual buffer boundaries, leading to memory corruption.

Attack Vector

The attack can be executed remotely over the network without requiring authentication or user interaction. An attacker could deliver malicious content containing specially crafted graphics data through various vectors such as:

• Malicious web pages rendering crafted images or canvas elements
• Malicious media files processed by Android's graphics subsystem
• Crafted documents or content shared through messaging applications
• Malicious advertisements containing embedded graphics

The vulnerability exploits the graphics rendering pipeline, meaning any application that processes untrusted graphics content could potentially trigger the flaw.

The integer overflow occurs during mask calculations in the emboss filter processing. When the calculated size overflows, subsequent memory operations write beyond allocated boundaries. Technical details of the fix can be found in the Android Skia Code Change.

Detection Methods for CVE-2024-43091

Indicators of Compromise

• Unexpected crashes or restarts in Android graphics-related services or system UI
• Anomalous memory consumption patterns in processes using Skia graphics rendering
• Unusual system behavior following interaction with untrusted graphic content
• Evidence of code execution from graphics rendering processes

Detection Strategies

• Monitor for crashes in Skia-related processes with memory corruption signatures
• Implement network-based detection for potentially malicious graphics content
• Deploy endpoint detection solutions capable of identifying exploitation attempts against graphics subsystems
• Review application logs for unusual graphics rendering failures or exceptions

Monitoring Recommendations

• Enable enhanced crash reporting to capture detailed information about graphics-related failures
• Monitor system logs for signs of memory corruption or unexpected process behavior
• Implement behavioral analysis to detect anomalous post-exploitation activity
• Track security patch levels across managed Android device fleets

How to Mitigate CVE-2024-43091

Immediate Actions Required

• Update affected Android devices to the November 2024 security patch level or later
• Prioritize patching for devices that regularly access untrusted content or networks
• Consider restricting access to untrusted web content on unpatched devices
• Implement network-level filtering for known malicious content where possible

Patch Information

Google has addressed this vulnerability in the November 2024 Android Security Bulletin. The fix involves correcting the integer overflow condition in the filterMask function within SkEmbossMaskFilter.cpp. Organizations should apply the security update with patch commit 0b628a960e74197ace9831ef0727f5ba7ab6ac10 to the Skia library component.

For detailed patch information, refer to the Android Security Bulletin November 2024 and the Android Skia Code Change.

Workarounds

• Limit exposure to untrusted content sources on unpatched devices
• Use mobile device management (MDM) solutions to enforce web browsing restrictions
• Implement network segmentation to isolate unpatched devices from untrusted networks
• Deploy SentinelOne Singularity Mobile to detect and prevent exploitation attempts on managed devices

# Check Android security patch level on device
adb shell getprop ro.build.version.security_patch
# Expected output for patched devices: 2024-11-01 or later