CVE-2026-73260

Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TLS certificate parser selected by MG TLS BUILTIN fails to verify that a long-form DER element length fits within the remaining certificate buffer. In mg der to tlv() and mg der next(), a peer-controlled length can advance the parser beyond the certificate and underflow the remaining uint32 t length, causing mg tls parse cert der() to continue walking an invalid pointer. An unauthenticated malicious TLS server, or a client presenting a certificate to a server configured for client certificates, can trigger an out-of-bounds read and denial of service during the handshake. This issue is fixed in version 7.23.