Microsoft has released security updates (SU) for Exchange Server version 2016 and 2019. The SUs are intended to close several vulnerabilities in the mail server software. The problem: Apparently the process fails, especially with German-speaking Exchange server instances, the update even paralyzes the systems temporarily. Microsoft cannot understand this.
The SUs are available for Exchange Server 2019 on the CU12 and CU13 cumulative update levels, as well as for CU23 on Exchange Server 2016. Even if there is currently no known active exploitation of the vulnerabilities reported by “security partners and found as part of Microsoft’s internal processes”. , advises Microsoft admins to install immediately. However, the company does not reveal which vulnerabilities are meant and only refers to the Security Update Guide. Exchange online installations are already protected against the vulnerabilities, and admins do not need to take any further steps.
No updates for German admins
Shortly after the release of the SUs, however, the first admins reported in the comments that the update could not be installed on them. In some cases, it even brings the respective Exchange server to its knees because it deactivates central Exchange services that then have to be reset manually. The reports have been piling up since yesterday. In addition, it became apparent that German or German-speaking servers in particular were affected. French admins also occasionally reported the problems, while US admins did not observe any error messages.
The cause of the problem in the SU has not yet been clarified, according to Microsoft employee Nino Bilic, the team is currently unable to reproduce the error. However, the log files of those affected indicate that the update released yesterday does not correctly recognize previously installed SUs. A script linked in the comments relieves admins of the necessary reconfiguration of the systems and services so that the affected servers can be started again. However, the script published by user bloodking does not help to install the security update that is actually necessary.
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