CVE-2024-39684: Tencent RapidJSON Privilege Escalation

CVE-2024-39684 Overview

Tencent RapidJSON is vulnerable to privilege escalation due to an integer overflow in the GenericReader::ParseNumber() function of include/rapidjson/reader.h when parsing JSON text from a stream. An attacker needs to send the victim a crafted file which needs to be opened; this triggers the integer overflow vulnerability (when the file is parsed), leading to elevation of privilege.

Critical Impact

This integer overflow vulnerability in the widely-used RapidJSON library can lead to privilege escalation when processing maliciously crafted JSON files, potentially compromising system integrity and confidentiality.

Affected Products

• Tencent RapidJSON (versions with vulnerable GenericReader::ParseNumber() implementation)
• Applications and products incorporating vulnerable RapidJSON library versions
• Microsoft products (see Microsoft CVE-2024-39684 Update)
• NetApp products (see NetApp Advisory NTAP-20240905-0003)

Discovery Timeline

• July 9, 2024 - CVE-2024-39684 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-39684

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). The flaw exists within the GenericReader::ParseNumber() function located in include/rapidjson/reader.h. When parsing numeric values from a JSON text stream, the function fails to properly validate integer boundaries, allowing specially crafted numeric values to trigger an integer overflow condition.

The attack requires local access and user interaction—the victim must open a maliciously crafted JSON file. Once the file is parsed by an application using the vulnerable RapidJSON library, the integer overflow can corrupt memory in a way that allows an attacker to escalate privileges on the target system. This can result in complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause is improper input validation within the GenericReader::ParseNumber() function. When parsing JSON numeric values, the function does not adequately check for integer overflow conditions before performing arithmetic operations. This allows an attacker to provide numeric values in a JSON document that cause the integer to wrap around, leading to unexpected memory states and potential exploitation.

Attack Vector

The attack vector for CVE-2024-39684 requires local access with user interaction:

1. Preparation: The attacker crafts a malicious JSON file containing specially constructed numeric values designed to trigger the integer overflow in ParseNumber()
2. Delivery: The attacker delivers this crafted JSON file to the victim through various means (email attachment, file sharing, malicious download, etc.)
3. Execution: The victim opens or processes the JSON file using an application that incorporates the vulnerable RapidJSON library
4. Exploitation: When the JSON parser attempts to process the malicious numeric values, the integer overflow is triggered
5. Privilege Escalation: The resulting memory corruption enables the attacker to escalate privileges on the target system

The vulnerability affects the number parsing functionality in the RapidJSON header-only C++ library. When the GenericReader::ParseNumber() function processes numeric values from a JSON stream without proper bounds checking, an integer overflow can occur. This can lead to subsequent memory corruption that an attacker can leverage for privilege escalation.

For detailed technical information, refer to the Microsoft CVE-2024-39684 Update and NetApp Advisory NTAP-20240905-0003.

Detection Methods for CVE-2024-39684

Indicators of Compromise

• Unusual JSON files with extremely large or malformed numeric values being processed by applications
• Applications using RapidJSON exhibiting unexpected crashes or memory corruption behaviors
• Privilege escalation events following JSON file processing activities
• Anomalous process behavior in applications known to use RapidJSON for JSON parsing

Detection Strategies

• Monitor for applications parsing unusually large JSON files or files with suspicious numeric content
• Implement application-level logging for JSON parsing errors and exceptions in RapidJSON-dependent applications
• Deploy endpoint detection solutions that can identify memory corruption exploitation attempts
• Use file integrity monitoring to detect suspicious JSON files being introduced to systems

Monitoring Recommendations

• Enable verbose logging for applications that process JSON data using RapidJSON
• Monitor process execution chains for signs of privilege escalation following document processing
• Implement behavioral analysis to detect anomalous activity patterns in JSON-parsing applications
• Review system audit logs for unexpected privilege changes correlated with file access events

How to Mitigate CVE-2024-39684

Immediate Actions Required

• Identify all applications and systems in your environment that use Tencent RapidJSON library
• Apply vendor patches as they become available from Microsoft, NetApp, and other affected vendors
• Implement network segmentation to limit the impact of potential privilege escalation
• Educate users about the risks of opening JSON files from untrusted sources

Patch Information

Organizations should monitor the following resources for patch information:

• Microsoft CVE-2024-39684 Update - Microsoft has released guidance for this vulnerability
• NetApp Advisory NTAP-20240905-0003 - NetApp security advisory with remediation information

Review the official advisories and apply the recommended updates to all affected products in your environment. Since RapidJSON is a widely-used library, ensure all applications incorporating this library are identified and updated accordingly.

Workarounds

• Restrict the processing of JSON files from untrusted sources until patches can be applied
• Implement application sandboxing to limit the impact of successful exploitation
• Use application whitelisting to prevent unauthorized code execution following privilege escalation
• Deploy file filtering solutions to scan and quarantine potentially malicious JSON files before processing

# Example: Identify applications using RapidJSON on Linux systems
# Search for applications linked against RapidJSON
find /usr -name "*.so" -exec sh -c 'strings {} 2>/dev/null | grep -q "rapidjson" && echo {}' \;

# Check for RapidJSON header files in development environments
find /usr/include /usr/local/include -name "rapidjson" -type d 2>/dev/null

# Monitor JSON file access (requires auditd)
auditctl -w /path/to/json/files -p r -k rapidjson_access