CVE-2026-45659 Microsoft SharePoint Server Deserialization of Untrusted Data
An authorized attacker can execute arbitrary code remotely via unsafe deserialization in Microsoft SharePoint Server.
- Exploited in the wild
- Since 1 Jul 2026
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-45659?
CVE-2026-45659 is a high-severity unsafe deserialization vulnerability in Microsoft Sharepoint Server, published on 22 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Weakness: CWE-502
Which versions are affected by CVE-2026-45659?
It affects 1 product.
Products include Microsoft Sharepoint Server.
How do I fix CVE-2026-45659?
No fix has been published for CVE-2026-45659 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 4 Jul 2026.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-45659 being exploited?
Yes. Attackers have exploited CVE-2026-45659 in the wild since at least 1 Jul 2026, including in ransomware campaigns.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in Microsoft Sharepoint Server
- CVE-2026-50522 Microsoft SharePoint Deserialization of Untrusted Data Vulnerability
- CVE-2026-58644 Microsoft SharePoint Deserialization of Untrusted Data
- CVE-2026-20963 Microsoft SharePoint Deserialization of Untrusted Data
- CVE-2025-53770 Microsoft SharePoint Deserialization of Untrusted Data
- CVE-2023-29357 Microsoft SharePoint Server Privilege Escalation
Sources
Also known as GHSA-w3mh-jmwv-56f3.