An exploitable off-by-one write vulnerability exists in the x509 certificate parsing functionality of wolfSSL library versions up to 3.10.2. A specially crafted x509 certificate can cause a single out of bounds byte overwrite resulting in potential certificate validation vulnerabilities, denial of service and possible remote code execution. In order to trigger this vulnerability, the attacker needs to supply a malicious x509 certificate to either server or client application using this library.