---
id: CVE-2026-73252
title: Mongoose is an embedded web server and network library
summary: >-
  Mongoose is an embedded web server and network library. Prior to 7.23, the
  built-in TLS stack selected by MG_TLS_BUILTIN in src/tls_builtin.c accepts a
  TLS 1.3 record whose decrypted size is exactly the 16-byte authentication tag
  with no…
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
  - CWE-191
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T20:17:58.753'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-73252'
references:
  - url: >-
      https://github.com/cesanta/mongoose/commit/758e301f0c9a9885c1b716195df5fe6d6ac9d53e
    label: security-advisories@github.com
  - url: 'https://github.com/cesanta/mongoose/releases/tag/7.23'
    label: security-advisories@github.com
  - url: >-
      https://github.com/cesanta/mongoose/security/advisories/GHSA-hq58-98f5-2wg3
    label: security-advisories@github.com
  - url: >-
      https://github.com/cesanta/mongoose/security/advisories/GHSA-hq58-98f5-2wg3
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
ingestedAt: '2026-10-14T19:49:57.615Z'
---

## Overview

Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TLS stack selected by MG_TLS_BUILTIN in src/tls_builtin.c accepts a TLS 1.3 record whose decrypted size is exactly the 16-byte authentication tag with no plaintext or ContentType byte. In mg_tls_recv_record(), the msgsz length check permits that record and the recv_len calculation underflows to SIZE_MAX, so a later handshake step treats stale buffer contents as a trusted message with an effectively unbounded length. An unauthenticated malicious TLS peer can trigger a heap out-of-bounds read before certificate or Finished validation, causing a remote denial of service. This issue is fixed in version 7.23.

## Remediation

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