CVE-2026-11404

High

Description

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.

SeverityHigh

CVSS7.5

Exploit probability—

ProductMongoose

PublishedJul 9, 2026

First seenJul 9, 2026

Weakness typeCWE-125Out-of-bounds read

How to fix

Update

Cesanta Mongoose7.22 or later

Patches

github.com/cesanta/mongoose/releases/tag/7.22

Affected products

Product	Affected versions	Fixed in
Cesanta Mongoose	v < 7.22	7.22

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