CVE-2023-40225

A flaw was found in HAProxy. Empty Content-Length headers are forwarded, which could cause an HTTP/1 server behind it to interpret the payload as an extra request. This may render the HTTP/1 server vulnerable to attacks in some uncommon cases.

Mitigation

This flaw can be mitigated by applying a rule to explicitly reject any requests with an empty Content-Lenght header. The following line can be added to any frontend configurations at the /etc/haproxy/haproxy.cfg file.

http-request deny if { hdr_len(content-length) 0 }