QlikView server communication interruptions following Microsoft Windows Domain Controller security updates

[Sonja_Bauernfeind]

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.

What can be done to mitigate this issue?

We've published an article to help address the issue. See QlikView server communication interruptions following Microsoft Windows RC4 cipher suite deprecation.

Information in the article is based on Microsoft's remediation steps and has been adjusted and expanded to include QlikView-specific instructions. For the original, see Detect and remediate RC4 usage in Kerberos | learn.microfot.com. 

What action is Qlik taking?

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.

Addendum

Microsoft Patches:

• Windows Server 2022 (DC): KB5082142
• Windows Server 2019 (DC): KB5082123
• Windows Server 2016 (DC): KB508208

If you have any questions, we're happy to assist. Reply to this blog post or take your queries to our Support Chat.

Thank you for choosing Qlik,
Qlik Support

[Eduardo_Monteiro]

Thanks for sharing!

[hugo_andrade]

Please place this as Featured content on Qlik Community for a few days, so it is visible right away.

It would help users facing this problem to quickly find the cause and resolution.

[JacovCohenQ]

Hi,
Can the links to the articles below resolve the issue described?

Disabling Kerberos encryption method RC4_HMAC_MD5 causes QlikView Server to disconnect
https://community.qlik.com/t5/Official-Support-Articles/Disabling-Kerberos-encryption-method-RC4-HMA...

Disable RC4 stream cipher in QlikView May 2022 (12.70) SR1 or higher
https://community.qlik.com/t5/Official-Support-Articles/Disable-RC4-stream-cipher-in-QlikView-May-20... 

[Eduardo_Monteiro]

We're able to get it fixed by following this article: Disabling Kerberos encryption method RC4_HMAC_MD5 ... - Qlik Community - 1715113

OS Version: 2019 Standard

QV Server Version: Sept 2025 SR1

When we went to check the LSP, all the cyphers were disabled, including RC4_MD5

All we did was to enable AES128 and AES256 at LSP, and also enable those for the service account and reboot the server.

I hope it works for you.

[DSCHNEID]

Great work Eduardo. Thanks for all your support over the years!!!

[Sonja_Bauernfeind]

Hello @hugo_andrade We're working on it. Thank you for your engagement! 

All the best,
Sonja

[JacovCohenQ]

@Eduardo_Monteiro 
Have you also checked to disable RC4 in QlikView according to https://community.qlik.com/t5/Official-Support-Articles/Disable-RC4-stream-cipher-in-QlikView-May-20...?

[Eduardo_Monteiro]

Yes, I did. I could not find the <add key="EnableRC4" value="true" /> neither SessionAlgorithm=Legacy. No changes were made regarding this article.

Thanks for sharing it!

[apierensv]

We did "RC4 change" & "enable AES128 and AES256 at LSP, and also enable those for the service account and reboot the server", it did not work, our production server is out of service for 9 days (!?).

[FabioSanchesRibeiro]

@apierensv try removing the server from the domain and adding it back again. This has resolved the issue in some environments.

Also, please check with the IT Team whether the patch has been applied to all servers and Domain Controllers. We have seen cases where not all Domain Controllers were updated. As a result, when authentication requests were handled by a non-updated server, the system worked, but when handled by an updated one, it failed since RC4 was no longer supported.

In some environments, the following solution has also worked:

https://community.qlik.com/t5/Official-Support-Articles/Disabling-Kerberos-encryption-method-RC4-HMA...