CVE-2023-37536: Xerces-C++ Buffer Overflow Vulnerability

CVE-2023-37536 Overview

CVE-2023-37536 is an integer overflow vulnerability in Apache Xerces-C++ 3.2.3, a validating XML parser library written in C++. This flaw allows remote attackers to cause out-of-bound memory access via specially crafted HTTP requests. The vulnerability affects multiple products that integrate with Xerces-C++, including HCL BigFix Platform and Fedora Linux distributions.

The integer overflow condition occurs when processing XML data, where arithmetic operations on integer values exceed the maximum storage capacity, causing the value to wrap around. This leads to incorrect memory allocation sizes and subsequent out-of-bounds memory access, potentially enabling information disclosure, denial of service, or in severe cases, arbitrary code execution.

Critical Impact

Remote attackers can exploit this integer overflow vulnerability via network-based HTTP requests to cause out-of-bounds memory access, potentially compromising system confidentiality, integrity, and availability.

Affected Products

• Apache Xerces-C++ version 3.2.3
• HCL BigFix Platform (multiple versions)
• Fedora 37

Discovery Timeline

• October 11, 2023 - CVE-2023-37536 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-37536

Vulnerability Analysis

This vulnerability stems from an integer overflow condition (CWE-190) that subsequently leads to a buffer overflow based on integer coercion errors (CWE-680). When the Xerces-C++ XML parser processes certain input data, integer arithmetic operations can overflow, resulting in unexpectedly small buffer allocations. When the application then attempts to write data to these undersized buffers, out-of-bounds memory access occurs.

The network-accessible nature of this vulnerability is particularly concerning as it can be triggered remotely through HTTP requests. Applications using Xerces-C++ to parse XML data from untrusted sources are at risk, especially web services and enterprise management platforms like HCL BigFix that process external XML content.

Root Cause

The root cause lies in improper integer handling within the Xerces-C++ library version 3.2.3. When processing XML input, certain size calculations involving integer values fail to properly validate against overflow conditions. This results in:

1. An integer value exceeding its maximum bounds and wrapping to a small positive value
2. Memory allocation based on the wrapped (incorrect) size
3. Subsequent operations writing beyond the allocated buffer boundaries

This is a classic integer overflow to buffer overflow vulnerability chain, where the initial arithmetic error cascades into memory corruption issues.

Attack Vector

The attack vector is network-based, requiring authenticated access with low complexity. An attacker can exploit this vulnerability by sending maliciously crafted HTTP requests containing XML data designed to trigger the integer overflow condition in Xerces-C++.

The exploitation mechanism involves crafting XML content with specific size values that, when processed by the vulnerable integer arithmetic operations, cause an overflow. This leads to memory corruption that could potentially allow attackers to:

• Read sensitive data from adjacent memory regions (information disclosure)
• Corrupt application state or crash the service (denial of service)
• Potentially achieve code execution in certain configurations

The vulnerability manifests during XML parsing operations when processing size-related fields. For technical details on the specific vulnerable code paths, refer to the HCL Tech Support Article and the Debian LTS Security Announcement.

Detection Methods for CVE-2023-37536

Indicators of Compromise

• Unexpected application crashes or segmentation faults in services using Xerces-C++ XML parsing
• Abnormal memory consumption patterns in XML processing components
• Malformed or unusually large XML payloads in HTTP request logs
• Core dumps or error logs indicating memory access violations in Xerces-C++ library functions

Detection Strategies

• Deploy network intrusion detection rules to identify malformed XML payloads targeting integer overflow conditions
• Monitor application logs for memory access violations or segmentation faults related to XML parsing
• Implement runtime memory protection tools to detect out-of-bounds access attempts
• Use software composition analysis (SCA) tools to identify vulnerable Xerces-C++ versions in your environment

Monitoring Recommendations

• Enable verbose logging for XML parsing operations in affected applications
• Configure memory protection mechanisms (ASLR, DEP) and monitor for bypass attempts
• Establish baseline metrics for XML processing performance to detect anomalies
• Monitor HCL BigFix Platform and other affected applications for unexpected behavior during XML operations

How to Mitigate CVE-2023-37536

Immediate Actions Required

• Inventory all systems running Apache Xerces-C++ 3.2.3 or applications that depend on it
• Apply vendor patches for HCL BigFix Platform as documented in the HCL support article
• Update Fedora systems using the packages referenced in the Fedora Package Security Notices
• Review and restrict network access to services that process XML content from untrusted sources

Patch Information

Patches are available from multiple vendors:

• HCL Technologies: Security updates for BigFix Platform are documented in the HCL Tech Support Article
• Fedora Project: Updated packages are available through the standard Fedora update channels as announced in the Fedora Package Announcements
• Debian: Security updates are available as detailed in the Debian LTS Security Announcement

Workarounds

• Implement input validation to reject excessively large or malformed XML documents before Xerces-C++ processing
• Deploy a web application firewall (WAF) with rules to filter suspicious XML payloads
• Restrict network access to vulnerable services, limiting exposure to trusted networks only
• Consider sandboxing or containerizing applications that must process untrusted XML content

# Example: Update Xerces-C++ on Fedora systems
sudo dnf update xerces-c

# Verify installed version after update
rpm -qa | grep xerces-c