Out-of-bounds Read in Cesanta Mongoose

CVE-2026-11404

Cesanta Mongoose before 7.22 contains an out-of-bounds read in the built-in TLS server function mg_tls_server_recv_hello(), which uses an attacker-controlled session_id_len byte from a TLS ClientHello as a buffer index without validating it against the length of received data. A remote, unauthenticated attacker can send a single crafted ClientHello with an oversized session id length to read past the receive buffer, crashing any HTTPS, MQTTS, or WSS service built on MG_TLS_BUILTIN.

Vulnerability class: Buffer Overflow

EPSS: 0.003 (27.9th percentile) — read the EPSS interpretation.