CVE-2022-23852: Libexpat Buffer Overflow Vulnerability

CVE-2022-23852 Overview

CVE-2022-23852 is a critical integer overflow vulnerability in Expat (libexpat), a widely-used XML parsing library. The vulnerability exists in the XML_GetBuffer function when configurations have a nonzero XML_CONTEXT_BYTES value. This signed integer overflow can lead to memory corruption, potentially enabling remote code execution or denial of service attacks against applications that process untrusted XML input.

Critical Impact

A signed integer overflow in XML_GetBuffer allows remote attackers to potentially execute arbitrary code or crash applications processing malicious XML content. Given libexpat's widespread use in numerous software products and systems, this vulnerability has significant impact across enterprise environments.

Affected Products

• libexpat_project libexpat (versions before 2.4.4)
• netapp clustered_data_ontap
• netapp oncommand_workflow_automation
• tenable nessus
• oracle communications_metasolv_solution
• debian debian_linux
• siemens sinema_remote_connect_server

Discovery Timeline

• 2022-01-24 - CVE-2022-23852 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2022-23852

Vulnerability Analysis

The vulnerability resides in the XML_GetBuffer function within the libexpat XML parsing library. When XML_CONTEXT_BYTES is configured with a nonzero value, the function performs arithmetic operations that can result in a signed integer overflow. This overflow condition occurs during buffer size calculations when processing XML data, leading to an incorrectly sized memory allocation.

The exploitation of this vulnerability does not require authentication and can be triggered remotely over a network connection. The attack complexity is low, meaning an attacker can reliably trigger the vulnerability without requiring specialized conditions or sophisticated techniques. Upon successful exploitation, an attacker could achieve complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause is classified as CWE-190 (Integer Overflow or Wraparound). The XML_GetBuffer function fails to properly validate integer arithmetic operations before performing memory allocations. When calculating buffer sizes, the function uses signed integer arithmetic without adequate overflow checks. If an attacker provides carefully crafted XML input that causes the buffer size calculation to exceed the maximum value of a signed integer, the result wraps around to a negative or unexpectedly small positive value, leading to undersized buffer allocation and subsequent memory corruption.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker can craft malicious XML content designed to trigger the integer overflow condition in XML_GetBuffer. When a vulnerable application parses this malicious XML input, the overflow occurs during buffer management operations.

The exploitation scenario involves:

1. The attacker identifies an application using a vulnerable version of libexpat (prior to 2.4.4)
2. The attacker crafts XML input that manipulates buffer size calculations in XML_GetBuffer
3. The malicious XML is delivered to the target application via any interface that accepts XML input
4. The signed integer overflow causes an undersized buffer allocation
5. Subsequent write operations overflow the buffer, potentially allowing arbitrary code execution

Technical details regarding the vulnerability fix can be found in the GitHub Pull Request for Expat.

Detection Methods for CVE-2022-23852

Indicators of Compromise

• Unexpected application crashes or segmentation faults in processes that parse XML content
• Anomalous memory consumption patterns in applications utilizing libexpat
• Core dumps indicating memory corruption in XML parsing routines
• Unusual network traffic containing malformed or excessively large XML payloads

Detection Strategies

• Deploy SentinelOne agents to detect exploitation attempts through behavioral analysis and memory protection mechanisms
• Implement network-based intrusion detection rules to identify malicious XML payloads targeting buffer overflow conditions
• Monitor application logs for parsing errors or exceptions related to XML processing
• Use software composition analysis (SCA) tools to identify applications with vulnerable libexpat versions

Monitoring Recommendations

• Enable enhanced logging for applications that process untrusted XML input
• Configure SentinelOne's Storyline technology to correlate events across XML parsing activities
• Establish baseline metrics for XML processing performance to detect anomalous behavior
• Implement file integrity monitoring on libexpat library files to detect unauthorized modifications

How to Mitigate CVE-2022-23852

Immediate Actions Required

• Update libexpat to version 2.4.4 or later immediately across all systems
• Inventory all applications and systems using libexpat to ensure comprehensive patching
• Prioritize patching for internet-facing systems and applications that process untrusted XML input
• Review vendor advisories from affected products including NetApp, Tenable, Oracle, Siemens, and Debian for product-specific patches

Patch Information

The vulnerability has been addressed in libexpat version 2.4.4. Multiple vendors have released patches for their affected products:

• Debian: Security updates available via Debian DSA-5073 Security Update and Debian LTS Security Notice
• NetApp: Advisory and patches available at NetApp Security Advisory NTAP-20220217-0001
• Oracle: Addressed in Oracle Critical Patch Update
• Tenable: Nessus updates detailed in Tenable Security Notification TNS-2022-05
• Siemens: SINEMA Remote Connect Server patches in Siemens Security Advisory
• Gentoo: Security updates via Gentoo GLSA 2022-09-24

Workarounds

• If immediate patching is not possible, consider disabling XML processing functionality in affected applications
• Implement strict input validation and size limits for XML content before parsing
• Deploy network-level controls to filter potentially malicious XML payloads
• Isolate vulnerable applications in segmented network zones with restricted access

# Verify libexpat version on Linux systems
expat -v 2>/dev/null || dpkg -l libexpat1 2>/dev/null || rpm -qa | grep expat

# Update libexpat on Debian/Ubuntu
sudo apt update && sudo apt upgrade libexpat1

# Update libexpat on RHEL/CentOS
sudo yum update expat