RuntimeException using Guess Headers ("header locating fail")

[jaredmcdonald]

Hi--first of all, thank you for the work that has gone into this very useful extension!

I'm getting a RuntimeException saying "can't find header" when using Guess Headers; apologies if I'm just doing something wrong here, but would greatly appreciate any help! Please let me know if I can provide any other information.

Steps to replicate

1. Set up the following request in the Repeater tab to portswigger.net:443

   GET /content/images/logos/portswigger-logo.svg HTTP/2
   Host: portswigger.net
   Accept: */*
   

2. Right-click and select Extensions > Guess headers
3. Leave default options and click OK
4. Go to Extender tab and see the following output:

   Using albinowaxUtils v0.22
   Loaded Param Miner v1.28
   CACHE_ONLY false
   Updating active thread pool size to 8
   Queued 1 attacks
   header locating fail: TCZqBcS13SA8QRCpW
   'GET /content/images/logos/portswigger-logo.svg HTTP/2
   Host: portswigger.net
   Accept: */*'
   Attack aborted by exception
   Error in thread: Can't find the header: TCZqBcS13SA8QRCpW. See error pane for stack trace.
   

   and the following in the Errors tab:

   java.lang.RuntimeException: Can't find the header: TCZqBcS13SA8QRCpW
   at burp.Utilities.setHeader(Utilities.java:949)
   at burp.HeaderNameInsertionPoint.buildBulkRequest(BurpExtender.java:407)
   at burp.ParamNameInsertionPoint.buildRequest(BurpExtender.java:306)
   at burp.PayloadInjector.probeAttack(PayloadInjector.java:152)
   at burp.ParamAttack.updateBaseline(ParamAttack.java:278)
   at burp.ParamAttack.<init>(ParamAttack.java:135)
   at burp.ParamGuesser.run(ParamGuesser.java:75)
   at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
   at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
   at java.base/java.lang.Thread.run(Thread.java:832)
   

Environment

• Mac OS 10.15.7 (Catalina)
• Burp Suite Community Edition v2021.6.2
• Param Miner v1.28