ingress-nginx: PATCH method dies with `enable-modsecurity: "true"` default configuration

Summary Observations: PATCH method with JSON request body sent to ingress receives no response bytes on connection and connection is left open.

Connection is closed only when NGINX ingress is bounced due to server reload (on change of ConfigMap, pod deletion … etc)

when Debug logging is enabled with SecDebugLog /dev/stdout SecDebugLogLevel 4

the debug log shows that phase 1 of the Modsecurity (a) recognized the “application/json”, and that (b) phase 2 assigned the JSON attributes into ARGS for subsequent scanning.

** Changing from “DetectOnly” to rule enforcement does not change the behavior. Adding the CRS ruleset does not change the behavior.

** PATCH method works correctly when enable-modsecurity: "false"

==================================== Version info:

• name: nginx-ingress repository: https://kubernetes-charts.storage.googleapis.com version: 1.33.5

kubectl version Server Version: version.Info{Major:“1”, Minor:“16”, GitVersion:“v1.16.9”, GitCommit:“a17149e1a189050796ced469dbd78d380f2ed5ef”, GitTreeState:“clean”, BuildDate:“2020-04-16T23:15:50Z”, GoVersion:“go1.13.9”, Compiler:“gc”, Platform:“linux/amd64”}