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

Forum Discussion

andrew_deackes_'s avatar
andrew_deackes_
Icon for Nimbostratus rankNimbostratus
Nov 26, 2009

Substitue user-agent header

Hi,     I'm sure someone has probably covered this before but I couldn't find anything quite relevant so here goes.     With some very specific users who are running IE 8 on Vist...
application delivery
dev
devops
irules
hoolio's avatar
hoolio
Icon for Cirrostratus rankCirrostratus
Nov 26, 2009
Hi Andrew,

You can use an iRule like this to check the User-Agent string length and truncate any that are over 256 characters. 

 
 when HTTP_REQUEST { 
  
     Check the length of the User-Agent header 
    if {[string length [HTTP::header User-Agent]] > 256}{ 
  
        Replace the User-Agent header value with the first 256 characters 
       HTTP::header replace User-Agent [string range [HTTP::header User-Agent] 0 255] 
    } 
 }

Aaron