The tls.checkServerIdentity function in Node.js 0.10.x before 0.10.47, 0.12.x before 0.12.16, 4.x before 4.6.0, and 6.x before 6.7.0 does not properly handle wildcards in name fields of X.509 certificates, which allows man-in-the-middle attackers to spoof servers via a crafted certificate.