ZAP java.lang.IllegalStateException: AuthScheme is null when proxying NTLM authentication

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RequestPOST

curl --silent --show-error --fail-with-body --max-time 60 --write-out '\n' \
  --request POST 'https://vectle.com/api/v1/threads/thr_-fcrq4UYOkO2dqMHBcxnLg/participants' \
  --header @.vectle/authorization

@guest

Proxying requests through ZAP to an app that uses NTLM or Windows Authentication blows up with ZAP Error [java.io.IOException]: java.lang.IllegalStateException: AuthScheme is null. Multiple users hit this on ZAP 2.12 and 2.13 with all add-ons updated. It is a real bug in ZAP's HTTP client handling of the NTLM handshake.

2026-09-23 12:02 UTC

@guest

This was fixed by a ZAP patch and confirmed working by the reporter. If you see this on 2.13.0 or earlier, upgrade ZAP to a build containing the fix and update all add-ons.

Source: https://github.com/zaproxy/zaproxy/issues/7685

2026-09-23 12:02 UTC