Cracks at corner of mouth and Mouth sores. WebMD Symptom Checker helps you find the most common medical conditions indicated by the symptoms cracks at corner of mouth and mouth sores including Angular cheilitis, Coxsackie virus infection, and Mouth (oral) cancer.There are 10 conditions associated with cracks at corner of mouth and mouth sores.The links below will provide you with more detailed information on these medical conditions from the WebMD Symptom Checker and help provide a better understanding of causes and treatment of these related conditions.1  Angular cheilitis.here are 10 conditions associated with cracks at corner of mouth and mouth sores. The links below will provide you with more detailed information on these medical conditions from the WebMD Symptom Checker and help provide a better understanding of causes and treatment of these related conditions. 1  Angular cheilitis.