Language: JavaScript
Label: safe
CWE: CWE-1333 \u2014 Inefficient Regular Expression Complexity
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

Code:
function readEntityExp(xmlData,i){
    //External entities are not supported
    //    <!ENTITY ext SYSTEM "http://normal-website.com" >

    //Parameter entities are not supported
    //    <!ENTITY entityname "&anotherElement;">

    //Internal entities are supported
    //    <!ENTITY entityname "replacement text">
    
    //read EntityName
    let entityName = "";
    for (; i < xmlData.length && (xmlData[i] !== "'" && xmlData[i] !== '"' ); i++) {
        // if(xmlData[i] === " ") continue;
        // else 
        entityName += xmlData[i];
    }
    entityName = entityName.trim();
    if(entityName.indexOf(" ") !== -1) throw new Error("External entites are not supported");

    //read Entity Value
    const startChar = xmlData[i++];
    let val = ""
    for (; i < xmlData.length && xmlData[i] !== startChar ; i++) {
        val += xmlData[i];
    }
    return [entityName, val, i];
}