Cisco has issued a warning that a decade-old vulnerability in its Adaptive Security Appliance (ASA) software is being actively exploited in the wild.The vulnerability, known as CVE-2014-2120, is a cross-site scripting (XSS) flaw affecting the WebVPN login page of the ASA software.Cisco has observed additional attempts to exploit the bug and US federal agencies have been advised to patch the vulnerability within three weeks.It is crucial for ASA users to promptly apply the patch, as cybercriminals often target old vulnerabilities that have working exploits.