CVE-2026-73256: Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by…

PriorityP265critical9.1CVSS 3.1

AVNACLPRNUINSUCHIHAN

EPSS

0.40%

33.8th percentile

Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.

Affected

1 ranges

Vendor	Product	Version range	Fixed in
cesanta	mongoose	< 7.22	7.22

Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.