AnyConnect 4.10.04065 broken browser proxy auth

[DAVIES604]

Hi Community.

The 2 latest releases of AnyConnect, so starting 4.10.04065, seem to break proxy authentication with both browsers we use, Edge/Chrome. I know that there was a SAML external browser feature added in this version, but this should only affect actual VPN authentication I believe. The VPN is a tunnel all setup, everything else works fine, but when attempting web access via our proxy, the browsers seem to not respond at all to the NTLM authorisation request, or this response is not finding its way over the tunnel. Any version before this and everything works fine. Has anyone else experienced anything like this? I'm struggling to see why/where AnyConnect would even get involved in this auth process. Any input appreciated. Thanks.

[DAVIES604 · Accepted solution]

Not sure this will help anyone as this may be very specific to our setup, but this problem only appears in release 4.10.04065 and 4.10.04071. Can't see any related bugs. All earlier releases and release 4.10.05085 (latest at time of writing) the problem doesn't happen.

[kishanpatel500]

I get the same issue. Packet capture also proves that the proxy is sending back a 407 with Proxy-Authenticate using NTLM, but Anyconnect keeps trying BASIC auth.

Tried on:
4.10.01075
4.10.04065
4.10.06079

I'll raise a case and see what TAC say.