---
id: CVE-2026-73253
title: Mongoose is an embedded web server and network library
summary: >-
  Mongoose is an embedded web server and network library. Prior to version 7.22,
  an on-path network attacker with a wildcard certificate for a parent domain
  can impersonate deeper subdomains to a client using the built-in TLS stack.
  The mg…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-295
vendor: cesanta
product: mongoose
affected:
  - mongoose < 7.22
patched:
  - mongoose 7.22
published: '2026-08-20'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T15:38:46.537'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-73253'
references:
  - url: >-
      https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71
    label: security-advisories@github.com
  - url: 'https://github.com/cesanta/mongoose/pull/3611'
    label: security-advisories@github.com
  - url: 'https://github.com/cesanta/mongoose/releases/tag/7.22'
    label: security-advisories@github.com
  - url: >-
      https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp
    label: security-advisories@github.com
  - url: >-
      https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73253.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-73253'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-73253'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
epss: 0.00344
epssPercentile: 0.27751
ingestedAt: '2026-09-09T21:22:45.545Z'
---

## Overview

Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.

## Affected

- `mongoose < 7.22`

## Remediation

Upgrade past the affected range:

- `mongoose 7.22`

## Vendor advisories

- **Red Hat VEX** · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73253.json)