In OISF LibHTP before 0.5.31, as used in Suricata 4.1.4 and other products, an HTTP protocol parsing error causes the http_header signature to not alert on a response with a single \r\n ending.
{ "binaries": [ { "binary_version": "0.5.15-1ubuntu0.1~esm1", "binary_name": "libhtp-dev" }, { "binary_version": "0.5.15-1ubuntu0.1~esm1", "binary_name": "libhtp1" } ] }
{ "binaries": [ { "binary_version": "1:0.5.26-1ubuntu0.1~esm1", "binary_name": "libhtp-dev" }, { "binary_version": "1:0.5.26-1ubuntu0.1~esm1", "binary_name": "libhtp2" } ] }