CVE-2024-38517: Tencent RapidJSON Privilege Escalation

CVE-2024-38517 Overview

CVE-2024-38517 is an integer underflow vulnerability in Tencent RapidJSON, a widely-used C++ JSON parsing library. The vulnerability exists in the GenericReader::ParseNumber() function located in include/rapidjson/reader.h. When parsing JSON text from a stream, an attacker can craft a malicious JSON file that triggers the integer underflow condition, potentially leading to privilege escalation on the affected system.

This vulnerability requires user interaction—specifically, the victim must open a crafted malicious file that triggers the parsing function. Upon successful exploitation, attackers can achieve elevation of privilege with high impact to confidentiality, integrity, and availability of the affected system.

Critical Impact

Integer underflow in JSON parsing can lead to privilege escalation when processing malicious JSON files, affecting applications using the RapidJSON library.

Affected Products

• Tencent RapidJSON library (versions prior to the security patch)
• Applications and software incorporating vulnerable RapidJSON versions
• Microsoft products (referenced in Microsoft Security Update Guide)
• NetApp products (referenced in NetApp Security Advisory)

Discovery Timeline

• July 9, 2024 - CVE-2024-38517 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-38517

Vulnerability Analysis

The vulnerability is classified as CWE-191 (Integer Underflow), a memory corruption flaw that occurs when an arithmetic operation results in a value smaller than the minimum allowed for the data type. In the context of RapidJSON, this occurs during the number parsing routine when processing JSON input streams.

Integer underflow vulnerabilities are particularly dangerous in C/C++ applications because they can lead to unexpected memory operations. When the underflow occurs in GenericReader::ParseNumber(), the resulting incorrect value can be used in subsequent memory operations, potentially allowing an attacker to manipulate program execution flow or gain elevated privileges.

The attack requires local access and user interaction—the victim must open a specially crafted JSON file. However, once triggered, the vulnerability can result in complete compromise of the affected system's confidentiality, integrity, and availability.

Root Cause

The root cause of CVE-2024-38517 is improper bounds checking in the GenericReader::ParseNumber() function within the include/rapidjson/reader.h header file. During the parsing of numeric values from JSON streams, arithmetic operations on integer values are performed without adequate validation to prevent underflow conditions.

When processing specially crafted numeric input that causes the integer value to wrap below zero (or below the minimum representable value for unsigned types), the parser proceeds with an incorrect value. This corrupted value can then influence memory allocation sizes, array indices, or other security-sensitive operations.

Attack Vector

The attack vector for CVE-2024-38517 is local, requiring the attacker to deliver a malicious JSON file to the victim. The exploitation scenario involves:

1. The attacker crafts a malicious JSON file containing numeric values designed to trigger the integer underflow
2. The victim opens the crafted file using an application that incorporates the vulnerable RapidJSON library
3. When the application parses the JSON content, the GenericReader::ParseNumber() function processes the malicious numeric value
4. The integer underflow occurs, corrupting internal state
5. The corrupted value leads to memory corruption or control flow hijacking
6. The attacker achieves privilege escalation on the affected system

The vulnerability manifests during JSON stream parsing in the number handling routine. Technical details and the security fix can be found in the GitHub Pull Request Commit.

Detection Methods for CVE-2024-38517

Indicators of Compromise

• Unusual JSON files with extremely large or malformed numeric values being processed by applications
• Unexpected crashes or memory errors in applications using RapidJSON during JSON parsing operations
• Application privilege escalation events following JSON file processing
• Abnormal memory allocation patterns in RapidJSON-dependent applications

Detection Strategies

• Implement file integrity monitoring for JSON files processed by critical applications
• Deploy endpoint detection and response (EDR) solutions to identify privilege escalation attempts
• Monitor for anomalous behavior in applications known to use RapidJSON for JSON parsing
• Use static analysis tools to identify RapidJSON version and flag vulnerable deployments
• Implement application whitelisting to control which applications can process external JSON files

Monitoring Recommendations

• Enable detailed logging for applications processing untrusted JSON input
• Monitor system calls for privilege escalation indicators following file parsing events
• Implement network segmentation to limit exposure of systems processing external JSON files
• Use SentinelOne's behavioral AI to detect exploitation attempts targeting memory corruption vulnerabilities
• Conduct regular software composition analysis (SCA) scans to identify vulnerable RapidJSON dependencies

How to Mitigate CVE-2024-38517

Immediate Actions Required

• Identify all applications and systems using the Tencent RapidJSON library in your environment
• Update RapidJSON to the patched version containing commit 8269bc2bc289e9d343bae51cdf6d23ef0950e001
• Review and apply vendor-specific patches for Microsoft and NetApp products as referenced in their security advisories
• Restrict processing of JSON files from untrusted sources until patches are applied
• Implement input validation for JSON files before parsing

Patch Information

The vulnerability has been addressed through a security patch available in the RapidJSON repository. The fix is documented in commit 8269bc2bc289e9d343bae51cdf6d23ef0950e001, which addresses the integer underflow condition in the GenericReader::ParseNumber() function.

Organizations should:

• Apply the patch from the GitHub Pull Request
• Review the Microsoft CVE Update Guide for Microsoft-specific guidance
• Consult the NetApp Security Advisory for NetApp product updates

Workarounds

• Implement strict input validation on JSON files before parsing with RapidJSON
• Limit JSON parsing to trusted sources only in production environments
• Deploy application sandboxing to contain potential exploitation attempts
• Use memory-safe parsing alternatives where possible for processing untrusted JSON input
• Apply principle of least privilege to applications processing JSON files to limit impact of successful exploitation

# Example: Verify RapidJSON version and check for vulnerable code
# Search for vulnerable function in codebase
grep -r "GenericReader::ParseNumber" /path/to/project/

# Check RapidJSON version in use
find /path/to/project -name "rapidjson.h" -exec grep -l "RAPIDJSON_MAJOR_VERSION" {} \;

# Update to patched version
git clone https://github.com/Tencent/rapidjson.git
cd rapidjson
git log --oneline | grep 8269bc2