Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls builtin.c, the mg tls init() function stores the bundle in tls->ca bundle der while tls->ca der.len remains zero, and mg tls recv cert() uses tls bundle find() to accept a Common Name match without calling mg tls verify cert signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.