Inconsistent interpretation of HTTP requests in Mongoose - CVE-2026-73256
Published: August 12, 2026
Vulnerability identifier: #VU142188
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-2026-73256
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to smuggle arbitrary requests.
The vulnerability exists due to inconsistent interpretation of HTTP requests in the http_cb() function in mongoose.c when processing HTTP/1.0 requests with a Transfer-Encoding: chunked header behind an HTTP/1.0 proxy. A remote attacker can send a specially crafted request to smuggle arbitrary requests.
Exploitation requires Mongoose to be deployed behind a proxy that uses HTTP/1.0 semantics for backend connections.
Affected software
Mongoose
How to mitigate CVE-2026-73256
Install security update from vendor's website.
Mongoose - update to 7.22