CVE-2020-0380: Google Android RCE Vulnerability

CVE-2020-0380 Overview

CVE-2020-0380 is a critical out-of-bounds write vulnerability in the allocExcessBits function within bitalloc.c of the Android operating system. The flaw stems from an incorrect bounds check that allows an attacker to write data beyond allocated memory boundaries. This vulnerability is particularly dangerous as it enables remote code execution without requiring any user interaction or additional execution privileges.

Critical Impact

This vulnerability allows attackers to achieve remote code execution on affected Android devices without user interaction, potentially compromising device integrity, confidentiality, and availability across Android versions 8.0 through 11.

Affected Products

• Google Android 8.0
• Google Android 8.1
• Google Android 9.0
• Google Android 10.0
• Google Android 11.0

Discovery Timeline

• September 17, 2020 - CVE-2020-0380 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-0380

Vulnerability Analysis

The vulnerability exists in the allocExcessBits function located in bitalloc.c, which is part of Android's audio processing components. The function fails to properly validate input boundaries before performing memory operations, creating a condition where data can be written outside the intended buffer space.

This out-of-bounds write vulnerability (CWE-787) can be triggered remotely over the network, requiring no authentication or user interaction. When exploited, an attacker can corrupt memory in a controlled manner, potentially overwriting critical data structures or function pointers. This memory corruption can then be leveraged to achieve arbitrary code execution within the context of the vulnerable process.

The vulnerability affects a wide range of Android versions spanning from Android 8.0 through Android 11.0, representing a significant portion of the Android device ecosystem at the time of disclosure.

Root Cause

The root cause of CVE-2020-0380 lies in improper bounds checking within the allocExcessBits function. When processing audio data, the function calculates buffer sizes and allocation requirements but fails to validate that write operations remain within allocated memory regions. This oversight allows carefully crafted input to trigger writes beyond buffer boundaries, leading to memory corruption.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker can exploit the flaw remotely without requiring local access to the device. The exploitation does not require any special privileges or user interaction, making it highly exploitable. A malicious audio file or stream processed by the vulnerable Android audio subsystem could trigger the out-of-bounds write, allowing an attacker to execute arbitrary code on the target device.

The vulnerable bitalloc.c component handles bit allocation for audio processing. When this component receives specially crafted input with malformed size parameters, the bounds check in allocExcessBits fails to catch the invalid values, resulting in memory writes outside the designated buffer area.

Detection Methods for CVE-2020-0380

Indicators of Compromise

• Unexpected crashes or restarts of Android media services or audio-related processes
• Abnormal memory consumption patterns in audio processing components
• Suspicious network traffic delivering potentially malicious audio data
• Evidence of code execution originating from audio processing contexts

Detection Strategies

• Monitor for unusual behavior in Android media frameworks and audio processing services
• Implement network-level inspection for malformed audio streams or files targeting Android devices
• Deploy endpoint detection solutions capable of identifying memory corruption exploitation attempts
• Analyze crash dumps for signs of out-of-bounds memory access in bitalloc.c related components

Monitoring Recommendations

• Enable detailed logging on Android devices for audio subsystem activities
• Monitor Mobile Device Management (MDM) solutions for signs of exploitation across managed devices
• Track security bulletin compliance to ensure devices are patched against CVE-2020-0380
• Implement network segmentation to limit exposure of vulnerable devices to untrusted network traffic

How to Mitigate CVE-2020-0380

Immediate Actions Required

• Apply the September 2020 Android Security Patch immediately on all affected devices
• Prioritize patching for devices exposed to untrusted networks or external content
• Review device inventory to identify all systems running Android versions 8.0 through 11.0
• Consider network-level protections to filter potentially malicious audio content until patching is complete

Patch Information

Google addressed CVE-2020-0380 in the Android Security Bulletin September 2020. The patch corrects the bounds checking logic in the allocExcessBits function within bitalloc.c to ensure memory write operations remain within allocated buffer boundaries.

Organizations should ensure all Android devices are updated to security patch level 2020-09-01 or later to remediate this vulnerability. The Android ID associated with this vulnerability is A-146398979.

Workarounds

• Limit device exposure to untrusted network content until patches can be applied
• Restrict processing of audio content from unknown or untrusted sources
• Implement Mobile Threat Defense (MTD) solutions to provide additional protection layers
• Enforce security policies through MDM to ensure devices maintain current security patch levels

# Verify Android security patch level
adb shell getprop ro.build.version.security_patch
# Expected output should be 2020-09-01 or later

# Check device build version
adb shell getprop ro.build.display.id