# CVE-2026-73257

## Summary

- **CVE ID:** CVE-2026-73257
- **Severity:** CRITICAL
- **CVSS Score:** 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)
- **CWE:** CWE-444
- **Published:** Aug 20, 2026
- **Last Modified:** Aug 20, 2026

## Description

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.

## Affected Products

- cesanta — mongoose (< 7.22)

## References

- [CNA](https://github.com/cesanta/mongoose/security/advisories/GHSA-5wfq-r6mr-wqp6)
- [CNA](https://github.com/cesanta/mongoose/pull/3611)
- [CNA](https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71)
- [CNA](https://github.com/cesanta/mongoose/releases/tag/7.22)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.48%
- **EPSS Percentile:** 40.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-12._