CVE-2022-25315: Libexpat Integer Overflow Vulnerability

CVE-2022-25315 Overview

CVE-2022-25315 is a critical integer overflow vulnerability affecting Expat (libexpat), a widely-used XML parsing library, in versions prior to 2.4.5. The vulnerability exists in the storeRawNames function, where an integer overflow condition can be triggered during XML parsing operations. Given libexpat's extensive use across numerous applications, operating systems, and enterprise products, this vulnerability has significant potential for widespread impact.

Critical Impact

This integer overflow vulnerability in the storeRawNames function can be exploited remotely without authentication, potentially leading to denial of service or arbitrary code execution on affected systems parsing malicious XML content.

Affected Products

• libexpat_project libexpat (versions prior to 2.4.5)
• Debian Linux 10.0 and 11.0
• Fedora 34 and 35
• Oracle HTTP Server 12.2.1.3.0 and 12.2.1.4.0
• Oracle ZFS Storage Appliance Kit 8.8
• Siemens SINEMA Remote Connect Server

Discovery Timeline

• 2022-02-18 - CVE-2022-25315 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2022-25315

Vulnerability Analysis

The vulnerability resides in the storeRawNames function within the libexpat XML parsing library. Integer overflow vulnerabilities occur when arithmetic operations produce a result that exceeds the maximum value the data type can hold, causing the value to wrap around to a smaller number. In this case, the overflow affects memory allocation calculations during XML parsing.

When parsing specially crafted XML input, the storeRawNames function fails to properly validate the size of raw name data before performing arithmetic operations. This can result in an undersized buffer being allocated, subsequently leading to heap-based buffer overflow conditions when the actual data is written to the insufficient buffer space.

The vulnerability is classified under CWE-190 (Integer Overflow or Wraparound), which describes the behavior when software performs calculations that result in a value outside the representable range. This commonly leads to memory corruption vulnerabilities that can be leveraged for code execution.

Root Cause

The root cause of CVE-2022-25315 is improper integer validation in the storeRawNames function. When processing XML element names, the function calculates required buffer sizes using integer arithmetic without adequate overflow checks. If an attacker provides XML input with carefully crafted element names or attributes that cause the size calculation to overflow, the resulting allocation will be smaller than required.

The fix, as documented in the GitHub Pull Request for Expat, adds proper bounds checking to prevent the integer overflow condition from occurring during the size calculation phase.

Attack Vector

The attack vector for CVE-2022-25315 is network-based, requiring no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Crafting malicious XML content designed to trigger the integer overflow in storeRawNames
2. Delivering the malicious XML to any application or service that uses a vulnerable version of libexpat for parsing
3. When the target application parses the XML, the integer overflow causes improper memory allocation
4. The subsequent buffer overflow can lead to denial of service through application crashes, or potentially arbitrary code execution if the attacker can control the overwritten memory contents

Common attack surfaces include web services accepting XML input, document processing applications, configuration parsers, and any network-facing service that processes XML data using libexpat.

Detection Methods for CVE-2022-25315

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications using libexpat during XML parsing operations
• Abnormally large or malformed XML documents being submitted to parsing services
• Memory corruption indicators in application logs associated with XML processing components
• System instability following XML document ingestion from untrusted sources

Detection Strategies

• Implement version detection scanning for libexpat versions prior to 2.4.5 across all systems and applications
• Deploy memory corruption detection tools to identify heap overflow conditions during XML parsing
• Monitor application crash dumps for signatures consistent with storeRawNames function failures
• Utilize SentinelOne's behavioral analysis capabilities to detect exploitation attempts targeting memory corruption vulnerabilities

Monitoring Recommendations

• Configure logging for XML parsing operations to capture details about malformed or unusually large documents
• Implement application performance monitoring to detect anomalous memory usage patterns during XML processing
• Review and audit all applications and dependencies that incorporate libexpat to ensure comprehensive coverage
• Leverage SentinelOne Singularity platform for real-time endpoint detection and response capabilities against exploitation attempts

How to Mitigate CVE-2022-25315

Immediate Actions Required

• Upgrade libexpat to version 2.4.5 or later immediately across all affected systems
• Identify all applications and services using vulnerable libexpat versions through software composition analysis
• Apply vendor-specific patches for Oracle HTTP Server, Siemens SINEMA Remote Connect Server, and other affected products
• Consider implementing input validation for XML content size as a defense-in-depth measure

Patch Information

The vulnerability is fixed in libexpat version 2.4.5 and later. Organizations should prioritize patching based on the following vendor advisories:

• libexpat: Upgrade to version 2.4.5 or later from the official project repository
• Oracle Products: Apply patches from the Oracle Critical Patch Update April 2022
• Debian Linux: Apply updates per Debian Security Advisory DSA-5085
• Siemens Products: Follow guidance in the Siemens Product Security Certificate
• Fedora: Apply package updates via standard package management
• NetApp: Review the NetApp Security Advisory NTAP-20220303-0008

Workarounds

• Implement strict input validation and size limits on XML documents before parsing where possible
• Deploy web application firewalls (WAF) with rules to detect and block oversized or malformed XML payloads
• Isolate XML processing services in sandboxed environments to limit potential blast radius
• Consider using alternative XML parsers for critical applications until patching is complete

# Configuration example
# Check installed libexpat version on Linux systems
dpkg -l | grep libexpat
rpm -qa | grep expat

# Update libexpat on Debian/Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade libexpat1

# Update libexpat on RHEL/CentOS/Fedora
sudo dnf update expat

# Verify the updated version (should be 2.4.5 or later)
expat_config --version