---
id: CVE-2026-73257
title: Mongoose is an embedded web server and network library
summary: >-
  Mongoose is an embedded web server and network library. Priro to version 7.22,
  a remote unauthenticated attacker can send an HTTP request containing both
  Content-Length and Transfer-Encoding: chunked. The cl_count and te_count
  checks in …
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-444
published: '2026-08-20'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:19:49.197'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-73257'
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-5wfq-r6mr-wqp6
    label: security-advisories@github.com
  - url: >-
      https://github.com/cesanta/mongoose/security/advisories/GHSA-5wfq-r6mr-wqp6
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00671
epssPercentile: 0.49878
ingestedAt: '2026-09-09T21:22:45.545Z'
---

## Overview

Mongoose is an embedded web server and network library. Priro to version 7.22, a remote unauthenticated attacker can send an HTTP request containing both Content-Length and Transfer-Encoding: chunked. The cl_count and te_count checks in the mg_http_parse() and http_cb() paths in src/http.c accept both headers and prioritize chunked encoding, while a Content-Length-preferring reverse proxy can use a different request boundary. This CL.TE desynchronization can inject requests that access or modify resources in another user context. This issue is fixed in version 7.22.

## Remediation

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