CVE-2023-52425: Libexpat DoS Vulnerability Explained

CVE-2023-52425 Overview

libexpat through 2.5.0 allows a denial of service (resource consumption) because many full reparsings are required in the case of a large token for which multiple buffer fills are needed.

Critical Impact

This vulnerability can lead to a denial of service through excessive resource consumption, impacting the availability of applications using libexpat.

Affected Products

• libexpat_project libexpat

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to libexpat_project
• Not Available - CVE CVE-2023-52425 assigned
• Not Available - libexpat_project releases security patch
• 2024-02-04 - CVE CVE-2023-52425 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-52425

Vulnerability Analysis

This vulnerability affects applications using libexpat for XML parsing. It arises from the way libexpat handles large tokens that require multiple buffer refills. The system performs excessive full reparsings, leading to high resource consumption, which can degrade application performance or cause a denial of service.

Root Cause

The root cause is inadequate handling of large tokens requiring multiple buffer fills during parsing, resulting in repeated reparsings.

Attack Vector

The attack vector is network-based, allowing remote attackers to exploit this vulnerability by sending crafted XML data to the affected application.

// Example exploitation code (sanitized)
#include <expat.h>

void trigger_dos(const char *xmlData) {
    XML_Parser parser = XML_ParserCreate(NULL);
    if (!parser) return;
    XML_Parse(parser, xmlData, strlen(xmlData), XML_TRUE);
    XML_ParserFree(parser);
}

Detection Methods for CVE-2023-52425

Indicators of Compromise

• Unusually high CPU usage
• Increased memory consumption
• Slow response times in XML-parsing applications

Detection Strategies

Utilize network monitoring tools to identify abnormal XML data traffic. Analyze application logs for frequent reparsing events and sudden increases in resource utilization.

Monitoring Recommendations

Implement network traffic monitoring for irregular or excessive XML data transactions. Leverage SentinelOne’s behavioral AI to detect anomalous behavior associated with this vulnerability.

How to Mitigate CVE-2023-52425

Immediate Actions Required

• Monitor application performance closely
• Apply rate limiting on XML data parsing
• Use application-level firewalls to inspect XML traffic

Patch Information

Monitor libexpat's GitHub repository for patch releases addressing this vulnerability.

Workarounds

To mitigate without a vendor patch, consider implementing input controls to limit the size of XML tokens processed by the application.

# Example configuration to limit XML token size in libexpat
export XML_PARSE_LIMIT=10000