Source: cve@mitre.org
An issue was discovered in ezXML 0.8.3 through 0.8.6. The function ezxml_decode, while parsing a crafted XML file, performs incorrect memory handling, leading to NULL pointer dereference while running strlen() on a NULL pointer.
ezXML, a library for parsing XML files, is vulnerable to a NULL pointer dereference due to incorrect memory handling. This allows attackers to craft malicious XML files that can cause a denial-of-service (DoS) by crashing applications using the vulnerable library. Successful exploitation can disrupt critical services and potentially lead to further compromise.
Step 1: Payload Delivery: The attacker crafts a malicious XML file containing specifically designed, malformed data or XML structures that trigger the vulnerability.
Step 2: File Ingestion: The targeted application, using the vulnerable ezXML library, attempts to parse the malicious XML file. This could be triggered by uploading the file, receiving it via a network connection, or accessing it from a storage location.
Step 3: Vulnerability Trigger: The ezxml_decode function processes the crafted XML, encounters the malformed data, and incorrectly handles memory allocation.
Step 4: NULL Pointer Dereference: Due to the memory handling error, a pointer is set to NULL. The code then attempts to dereference this NULL pointer, typically by calling strlen() on it.
Step 5: Application Crash: The attempt to dereference the NULL pointer causes a segmentation fault, leading to the application crashing and resulting in a denial-of-service condition.
The vulnerability lies within the ezxml_decode function of the ezXML library. When parsing a specially crafted XML file, the function fails to properly handle memory allocation and deallocation. Specifically, the code attempts to use strlen() on a pointer that has been set to NULL. This occurs because of a flaw in how the library handles certain XML structures or malformed data within the XML file. The root cause is a lack of proper input validation and error handling when processing the XML data, leading to a NULL pointer dereference. This results in a segmentation fault and application termination, effectively creating a denial-of-service condition. There is no evidence of a buffer overflow or other memory corruption vulnerabilities, only a crash.
There is no specific APT or malware directly associated with this vulnerability. However, any threat actor seeking to disrupt services could leverage this vulnerability. The impact is a DoS, which can be used by any attacker. This vulnerability is not listed on the CISA KEV.
Monitor application logs for segmentation faults or crashes related to XML parsing.
Analyze network traffic for unusual XML file uploads or downloads.
Implement intrusion detection system (IDS) rules to identify attempts to exploit the vulnerability based on the structure of the XML file.
Monitor system resource usage (CPU, memory) for spikes during XML parsing operations, which could indicate a DoS attempt.
Examine core dumps or crash reports for evidence of the ezxml_decode function being involved in the crash.
Upgrade to ezXML version 0.8.7 or later, which contains a fix for the vulnerability.
If upgrading is not immediately possible, implement input validation to filter and sanitize XML files before they are parsed by the vulnerable library. This can include validating the XML structure and content against a known schema.
Implement rate limiting on XML parsing requests to mitigate the impact of a DoS attack.
Use a web application firewall (WAF) to filter malicious XML payloads.
Monitor and patch all applications that use the ezXML library.