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Microsoft Patches SharePoint RCE Flaw CVE-2026-45659
Microsoft has released a new security update to patch a vulnerability affecting multiple versions of SharePoint: CVE-2026-45659. This issue can lead to remote code execution (RCE) on the SharePoint server. Here’s what you need to know.
SharePoint Server affected by CVE-2026-45659
The security flaw CVE-2026-45659 is considered important and has been assigned a CVSS score of 8.8 out of 10. It stems from a data deserialization issue in Microsoft SharePoint Server.
According to Microsoft, this vulnerability allows remote code execution on the SharePoint server. To exploit it, an attacker must be authenticated, as Microsoft explains in its security advisory: "In a network-based attack, an authenticated attacker with at least site member permissions (PR:L) could execute code remotely on the SharePoint server."
Which SharePoint versions are affected?
CVE-2026-45659 affects several SharePoint versions. Microsoft has made security updates available for the following releases:
- SharePoint Server Subscription Edition (SE)
- SharePoint Server 2019
- SharePoint Enterprise Server 2016
"The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers using either version must install the security update to protect against this vulnerability.", it says.
According to Microsoft, this vulnerability is not being exploited at the moment. It also notes that the flaw is "less likely to be exploited", though things can move very quickly in cybersecurity.
As a reminder, last month Microsoft also had to fix a spoofing flaw affecting Microsoft SharePoint Server (CVE-2026-32201), which was actively being exploited by cybercriminals.
Links to the security updates are listed on this page on the MSRC website.
