CVE-2024-25062: Xmlsoft Libxml2 Use-After-Free Vulnerability

CVE-2024-25062 Overview

CVE-2024-25062 is a use-after-free vulnerability discovered in libxml2, a widely-used XML parsing library. The vulnerability exists in versions prior to 2.11.7 and in the 2.12.x branch before 2.12.5. When using the XML Reader interface with DTD validation and XInclude expansion enabled, processing specially crafted XML documents can trigger a use-after-free condition in the xmlValidatePopElement function, potentially leading to denial of service.

Critical Impact

This use-after-free vulnerability can be exploited remotely without authentication to cause denial of service conditions in applications using libxml2 for XML parsing with DTD validation and XInclude expansion.

Affected Products

• xmlsoft libxml2 versions before 2.11.7
• xmlsoft libxml2 versions 2.12.x before 2.12.5

Discovery Timeline

• 2024-02-04 - CVE-2024-25062 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-25062

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption issue that occurs when a program continues to use a pointer after the memory it references has been freed. In the context of libxml2, the vulnerability manifests specifically within the xmlValidatePopElement function when certain XML processing features are combined.

The attack can be executed over the network without requiring any privileges or user interaction. The primary impact is on system availability, as successful exploitation leads to denial of service conditions. The vulnerability does not directly compromise data confidentiality or integrity, but the use-after-free condition could potentially be leveraged for more severe attacks depending on the memory layout and application context.

Root Cause

The root cause lies in improper memory management within libxml2's XML validation logic. When the XML Reader interface processes documents with both DTD validation and XInclude expansion enabled, a race condition or improper object lifecycle management causes the xmlValidatePopElement function to reference memory that has already been deallocated. This occurs because the validation context and XInclude processing interact in ways that weren't properly accounted for in the memory management logic.

Attack Vector

An attacker can exploit this vulnerability by crafting a malicious XML document that triggers the specific code path combining DTD validation and XInclude expansion. The attack requires no authentication and can be delivered remotely to any application that:

1. Uses the libxml2 XML Reader interface
2. Has DTD validation enabled
3. Has XInclude expansion enabled
4. Processes untrusted XML input

The crafted XML document would contain elements designed to manipulate the parsing state in a way that causes premature memory deallocation while references to that memory are still active. When the xmlValidatePopElement function subsequently attempts to access this freed memory, it triggers undefined behavior that typically manifests as a crash, causing denial of service. Technical details about the specific triggering conditions can be found in the GNOME libxml2 Issue Tracker.

Detection Methods for CVE-2024-25062

Indicators of Compromise

• Application crashes or segmentation faults in processes using libxml2 for XML parsing
• Unexpected termination of services that process XML documents with DTD validation
• Memory access violations logged in system crash dumps pointing to libxml2 functions
• Repeated service restarts indicating potential exploitation attempts

Detection Strategies

• Monitor application logs for crashes related to XML parsing operations, specifically in xmlValidatePopElement or related validation functions
• Implement runtime memory corruption detection tools such as AddressSanitizer in development and staging environments
• Deploy endpoint detection solutions capable of identifying use-after-free exploitation patterns
• Audit systems for vulnerable libxml2 versions using software composition analysis tools

Monitoring Recommendations

• Enable crash dump analysis for applications using libxml2 to identify exploitation attempts
• Configure alerting for unusual patterns of application restarts in XML processing services
• Monitor network traffic for anomalous XML documents being submitted to vulnerable endpoints
• Implement application-level logging for XML parsing errors and validation failures

How to Mitigate CVE-2024-25062

Immediate Actions Required

• Upgrade libxml2 to version 2.11.7 or later for the 2.11.x branch
• Upgrade libxml2 to version 2.12.5 or later for the 2.12.x branch
• Identify all applications and services in your environment that depend on libxml2
• Prioritize patching for internet-facing services that process untrusted XML input

Patch Information

Security patches addressing this vulnerability are available in libxml2 versions 2.11.7 and 2.12.5. The patches correct the memory management issues in the xmlValidatePopElement function to prevent use-after-free conditions during combined DTD validation and XInclude expansion operations.

For detailed patch information, refer to the GNOME libxml2 Tags page for official releases. Additional vendor-specific advisories are available from Debian LTS Security Announcement and NetApp Security Advisory.

Workarounds

• If patching is not immediately possible, consider disabling XInclude expansion when processing untrusted XML documents
• Alternatively, disable DTD validation for untrusted input if XInclude functionality is required
• Implement input validation to reject XML documents containing XInclude directives from untrusted sources
• Deploy web application firewalls configured to inspect and filter potentially malicious XML payloads

# Check installed libxml2 version
xml2-config --version

# For Debian/Ubuntu systems, update libxml2
sudo apt update && sudo apt upgrade libxml2

# For RHEL/CentOS systems
sudo yum update libxml2

# Verify the updated version
xml2-config --version