The Kaspersky AV engine allows customers to enable certain enhanced scanning features, these are configurable from the CAS GUI
Services -> AV Scanning Behavior - > Engine Settings
Enabling these features may cause certain web sites to fail to load.
ICAP Error (icap_error)
An error occurred while performing an ICAP operation: Anti-virus engine error (26:0x80070057); File: noname; Sub File: ; Vendor: Kaspersky Labs; Engine version 126.96.36.199; Pattern version: 180720.133800.11863587; Pattern date: 2018/07/20 13:38:00
For assistance, contact your network support team.
The error is caused by the website returning non-RFC2616 characters in response headers.
This is not obvious from a pcap
But is easy to see in a browsers developer tools
Content Analysis System running CAS 1.3 - 188.8.131.52
Advanced Secure Gateway running SGOS 6.6 - 184.108.40.206
This issue is first addressed in CAS 220.127.116.11 and above as well as ASG 18.104.22.168 and above.
There are a few workarounds to address this concern:
Alternatively contacting the administrator of the web site and asking that they not use non RFC complaint characters in the headers will resolve the issue.