Inconsistent interpretation of HTTP requests in Mongoose - CVE-2026-73257
Published: August 12, 2026
Vulnerability identifier: #VU142187
CSH Severity: High
CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-73257
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information and modify application state.
The vulnerability exists due to inconsistent interpretation of HTTP requests in mg_http_parse() and http_cb() when processing HTTP requests containing both Content-Length and Transfer-Encoding headers. A remote attacker can send a specially crafted request through a CL-preferring proxy to disclose sensitive information and modify application state.
Exploitation requires Mongoose to be deployed behind a reverse proxy that uses Content-Length to determine request boundaries.
Affected software
Mongoose
How to mitigate CVE-2026-73257
Install security update from vendor's website.
Mongoose - update to 7.22