Source: cve@mitre.org
An issue was discovered in ezXML 0.8.3 through 0.8.6. The function ezxml_decode, while parsing crafted a XML file, performs incorrect memory handling, leading to a heap-based buffer over-read in the "normalize line endings" feature.
ezXML, a library for parsing XML files, is vulnerable to a heap-based buffer over-read due to incorrect memory handling in its ezxml_decode function. This vulnerability allows attackers to craft malicious XML files that, when parsed, can lead to the disclosure of sensitive information or potentially remote code execution if chained with other vulnerabilities. Successful exploitation could lead to data breaches and system compromise.
Step 1: Payload Delivery: The attacker crafts a malicious XML file containing specially crafted input designed to trigger the vulnerability.
Step 2: File Parsing: The vulnerable application, using the ezXML library, attempts to parse the malicious XML file.
Step 3: Vulnerability Trigger: The ezxml_decode function, while processing the XML, encounters the crafted input and attempts to normalize line endings.
Step 4: Buffer Over-read: Due to the incorrect buffer size calculation, the line ending normalization process reads beyond the allocated memory, leading to a heap-based buffer over-read.
Step 5: Information Disclosure/Potential Exploitation: The over-read can potentially leak sensitive information stored in adjacent memory. In some scenarios, this information could be leveraged to achieve remote code execution if combined with other vulnerabilities or used to bypass security measures.
The vulnerability lies within the ezxml_decode function of the ezXML library, specifically in the 'normalize line endings' feature. The function incorrectly calculates the size of the buffer when handling line endings (e.g., \r, \n). This leads to a heap-based buffer over-read when processing a specially crafted XML file. The over-read occurs because the code attempts to read beyond the allocated memory boundaries. This can expose sensitive data residing in adjacent memory locations. The root cause is a flawed calculation of the buffer size during the line ending normalization process, which fails to account for the potential expansion of the data due to the normalization. This incorrect calculation allows the read operation to access memory outside the intended bounds, leading to the over-read.
While no specific APT groups are definitively linked to the exploitation of this vulnerability, its nature makes it attractive to various threat actors. The vulnerability's potential for information disclosure makes it a valuable tool for reconnaissance and initial access. CISA KEV status: Not listed.
Monitor file system activity for the creation or modification of XML files, especially those originating from untrusted sources.
Analyze network traffic for XML files being transmitted to or from the vulnerable application.
Implement intrusion detection systems (IDS) with signatures that detect the specific patterns of the crafted XML payloads.
Monitor application logs for errors or unexpected behavior during XML parsing, such as segmentation faults or memory access violations.
Use memory analysis tools (e.g., Valgrind, AddressSanitizer) to identify memory access violations during XML parsing.
Upgrade to ezXML version 0.8.7 or later, which contains a fix for the vulnerability.
Implement input validation to sanitize and validate all XML files before parsing them.
Apply the principle of least privilege, ensuring that the application runs with the minimum necessary permissions.
Regularly update all software and libraries to the latest versions.
Employ a Web Application Firewall (WAF) to filter malicious XML payloads.