CVE-2020-0187: Google Android Information Disclosure Flaw

CVE-2020-0187 Overview

CVE-2020-0187 is a cryptographic vulnerability in Google Android affecting the engineSetMode function in BaseBlockCipher.java. The vulnerability arises from an incomplete comparison that can result in an incorrect cryptographic algorithm being selected during cipher operations. This flaw could lead to local information disclosure without requiring additional execution privileges or user interaction.

Critical Impact

A local attacker could exploit this incomplete comparison vulnerability to cause the system to select an inappropriate cryptographic algorithm, potentially leading to sensitive information disclosure on affected Android 10 devices.

Affected Products

• Google Android 10.0

Discovery Timeline

• 2020-06-11 - CVE CVE-2020-0187 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-0187

Vulnerability Analysis

This vulnerability exists within the engineSetMode method of the BaseBlockCipher.java class in Android's cryptographic implementation. The root cause is an incomplete string comparison when determining which cipher mode to use for block cipher operations. When the mode string comparison fails to fully validate the input, the system may default to or select an unintended cryptographic algorithm.

The flaw allows exploitation through local access to the device. An attacker with local access can trigger the vulnerable code path without requiring any special privileges or user interaction. The attack surface is localized to the device itself, making this a local vector vulnerability that could expose confidential information stored on the device.

Root Cause

The incomplete comparison in engineSetMode stems from insufficient validation of the cipher mode parameter. When processing mode strings, the comparison logic does not fully evaluate all characters or conditions, potentially causing a fallback to an incorrect algorithm. This type of logic error in cryptographic implementations can have severe consequences, as the security guarantees of encryption depend entirely on using the correct algorithms with proper parameters.

Attack Vector

The vulnerability requires local access to an Android 10 device. An attacker can exploit this flaw through:

1. A malicious application installed on the device that invokes cryptographic operations
2. Another local process that can interact with the Android cryptographic framework
3. Direct access to the device to execute code that triggers the vulnerable comparison

The exploitation does not require elevated privileges or user interaction, making it a relatively straightforward attack once local access is obtained. The impact is limited to confidentiality breaches through information disclosure.

Detection Methods for CVE-2020-0187

Indicators of Compromise

• Unusual cryptographic operations logged on Android 10 devices
• Applications accessing sensitive data through unexpected cipher modes
• Anomalous behavior in apps that perform encryption/decryption operations
• Log entries indicating cipher mode selection errors or fallbacks

Detection Strategies

• Monitor system logs for anomalies in cryptographic operations within BaseBlockCipher.java
• Implement application-level monitoring to detect unusual cipher mode requests
• Use endpoint detection solutions to identify applications exploiting cryptographic flaws
• Review Android security patch levels to identify unpatched devices

Monitoring Recommendations

• Enable verbose logging for cryptographic operations on Android devices in enterprise environments
• Deploy mobile device management (MDM) solutions to track security patch compliance
• Implement behavioral analysis to detect apps performing suspicious cryptographic activities

How to Mitigate CVE-2020-0187

Immediate Actions Required

• Apply the Android security patch from the June 2020 security bulletin immediately
• Verify all Android 10 devices in your environment are updated to the latest security patch level
• Review installed applications for any suspicious cryptographic behavior
• Consider restricting installation of untrusted applications until patches are applied

Patch Information

Google addressed this vulnerability in the Android Security Bulletin June 2020. The fix corrects the incomplete comparison logic in the engineSetMode method to ensure proper cryptographic algorithm selection. Organizations should prioritize applying this security update to all affected Android 10 devices.

The vulnerability is tracked internally by Google as Android ID: A-148517383.

Workarounds

• Limit installation of third-party applications on affected devices until patching is complete
• Implement network-level monitoring to detect potential data exfiltration
• Use enterprise MDM solutions to enforce security policies and restrict app installations
• Consider temporary isolation of unpatched devices from sensitive data access