---
id: CVE-2026-11404
title: >-
  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…
summary: >-
  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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-125
published: '2026-07-09'
updated: '2026-08-29'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11404'
references:
  - url: 'https://github.com/cesanta/mongoose'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/cesanta/mongoose/releases/tag/7.22'
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00608
epssPercentile: 0.46757
ingestedAt: '2026-08-29T14:37:55.188Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.