Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

T_Rajneesh's avatar
T_Rajneesh
Icon for Nimbostratus rankNimbostratus
May 06, 2019

How to block /_async/* and /wls-wsat/* at the F5 Load Balancer for Oracle WebLogic server.

Critical remote code execution vulnerability found in Oracle WebLogic server.   Can you please suggest how to block /_async/* and /wls-wsat/* at the F5 Load Balancer.   Is it possible do it v...
application delivery
big-ip
irules
security
Dario_Garrido's avatar
Dario_Garrido
Icon for Noctilucent rankNoctilucent
May 06, 2019

Three ways to do it...

Using 'contains':

when HTTP_REQUEST {
    if {{ [string tolower [HTTP::uri]] contains "_async" } || { [string tolower [HTTPS::uri]] contains "wls-wsat" }} {
        drop
    }
}

Using 'starts_with'

when HTTP_REQUEST {
    if {{ [string tolower [HTTP::uri]] starts_with "/_async" } || { [string tolower [HTTP::uri]] starts_with "/wls-wsat" }} {
        drop
    }
}

But the best option is to configure a policy in LTM which has exactly the same options I'm using in the previous iRules and is faster.

REF - https://devcentral.f5.com/articles/ltm-policy

KR, Dario.

davidfisher's avatar
davidfisher
Icon for Cirrus rankCirrus
Sep 02, 2021

is this a good way to use irules to just block a CVE? cant we use asm to do this?

This irule is creating a problem with the f5 maintenance page irule which we are using.

I have these irules applied, and the moment I add the one with maintenance page, the connection just starts dropping..

=-=-=
### MAINT PAGE IRULE
when HTTP_REQUEST {
if { [active_members XXX_pool] == 0 }
{
   HTTP::respond 200 content [ifile get main-image]
 
}
 }
 
 
 ******
 
 when HTTP_REQUEST {
if {[HTTP::has_responded]}{return}
	if { [HTTP::path] equals "/" } {
		HTTP::respond 302 Location "https://testing.com/testingweb/common/tesnet.jsf" Strict-Transport-Security "max-age=16070400"
		return
	}
}
 
 
******
 
when HTTP_REQUEST { 
   set uri [string tolower [HTTP::uri]]
   if { ( $uri contains "/wls-wsat/") or ( $uri contains "/_async/") }  { 
         drop
      }
}
 
=-=-=