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CVE-2026-45659: Microsoft SharePoint Remote Code Execution Vulnerability

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-07-01
• EPSS: 80.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-22 · updated 2026-08-11
• Weakness: CWE-502

Description

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

Summary

CVE-2026-45659 is a deserialization of untrusted data flaw in Microsoft SharePoint Server that lets an authorized attacker execute code over the network (CVSS 8.8). It is listed in CISA's Known Exploited Vulnerabilities catalog with active exploitation, and EPSS puts the 30-day exploitation probability at 80.2%. Affected is Microsoft SharePoint Server, fixed in version 16.0.19725.20280. Apply the vendor mitigations and update to the fixed build per CISA BOD 26-04 guidance, and discontinue use if mitigations are unavailable.

CVE-2026-45659 ثغرة إزالة تسلسل لبيانات غير موثوقة في Microsoft SharePoint Server تتيح لمهاجم مصرّح له تنفيذ تعليمات برمجية عبر الشبكة (CVSS 8.8). وهي مدرجة في كتالوج CISA للثغرات المعروفة باستغلالها مع استغلال نشط، وتبلغ احتمالية الاستغلال خلال 30 يوماً وفق EPSS نسبة 80.2%. المنتج المتأثر هو Microsoft SharePoint Server، وقد تم إصلاحها في الإصدار 16.0.19725.20280. طبّق تخفيفات الجهة المصنّعة وحدّث إلى الإصدار المُصلح وفق إرشادات CISA BOD 26-04، وتوقف عن استخدام المنتج إذا لم تتوفر التخفيفات.

Affected products

• Microsoft SharePoint Server: before 16.0.19725.20280; 2016, 2019 — fixed in 16.0.19725.20280
• Microsoft SharePoint Server Subscription Edition: from 16.0.0 before 16.0.19725.20280 — fixed in 16.0.19725.20280
• Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5552.1002 — fixed in 16.0.5552.1002
• Microsoft SharePoint Server: from 16.0.0 before 16.0.10417.20128 — fixed in 16.0.10417.20128

How to fix

Upgrade to a fixed version: Microsoft SharePoint Server 16.0.19725.20280; Microsoft SharePoint Server Subscription Edition 16.0.19725.20280; Microsoft Sharepoint Enterprise Server 2016 16.0.5552.1002; Microsoft SharePoint Server 16.0.10417.20128. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45659

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