A flaw in Node.js TLS hostname verification allows a certificate with only a DNS SAN to authenticate an IP endpoint when the client connects using a non-canonical IPv4 spelling, such as "0177.0.0.1", "0x7f.0.0.1", "2130706433" or "127.1". "tls.checkServerIdentity()" did not classify these hosts as IP addresses, but normalized them to their canonical form and matched the result against the certificate DNS names. A certificate containing "DNS:127.0.0.1" and no "IP Address:127.0.0.1" SAN was therefore accepted, while the same certificate is correctly rejected for "127.0.0.1". Exploitation requires a certificate with a numeric DNS SAN issued by a CA trusted by the client, and a platform resolver that accepts these spellings, such as glibc. This vulnerability affects Node.js 26.x, 24.x, and 22.x.