Edited May 4th, 2026: Added mitigation article, published on the 4th of May.
Beginning on April 14, 2026, multiple QlikView customers experienced outages and intermittent disruptions within their QlikView environments. These incidents coincided with the deployment of Microsoft’s April 2026 security patches to Domain Controllers, which affected QlikView Server Service (QVS) communications over port 4747.
The Microsoft patches introduced changes targeting Kerberos authentication and RC4 encryption. See Addendum for a list of patches. As a result, QlikView environments where RC4 remained enabled (such as at the domain account or Windows server level) became unstable or non-functional.
The impact on QlikView may include, but is not limited to:
Failed QlikView Distribution Server distribution tasks with an error code indicating an Authentication Failure.
"No Server" message on the QlikView AccessPoint with an error message in the Web server log indicating that the Web server cannot connect to the QlikView Server.
Failed Qlik NPrinting distributions to QlikView using a QVP Connection.
Problems accessing the QlikView Server settings from the QlikView Management Console, or failures for the QlikView Server to come online after a restart.
RC4 support was deprecated starting with the May 2024 release of QlikView. The root cause in these cases stems from legacy configurations where RC4 remained enabled in the environment, rather than a defect in QlikView itself. No code changes are planned at this time, though improvements to diagnostic logging are under consideration.
