CVE-2018-18509

CVE-2018-18509 is a medium-severity vulnerability in Mozilla Thunderbird versions prior to 60.5.1, where a flaw in S/MIME signature verification allows an attacker to craft emails with arbitrary content that appear to have a valid digital signature. The attack vector is network-based with low complexity, and the primary impact is a low integrity compromise, as an attacker can deceive recipients about the authenticity of email content. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this vulnerability.