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CVE-2026-45659 - Microsoft SharePoint Deserialization RCE

Consultant-Style Cybersecurity Report
Professional vulnerability assessment report for SharePoint deserialization risk, including executive summary, technical impact, remediation, and mitigation strategy.

Report Type Sanitized OWASP WSTG Focus Area


📍 Report Snapshot

Field Details
Report Type Vulnerability Assessment Report
Engagement Context Security Research
Primary Focus Enterprise Collaboration Security
Audience Security teams, engineering teams, hiring managers
Output Style Executive summary, technical analysis, business impact, remediation roadmap
Publication State Sanitized for public portfolio review

Important

This report is intentionally sanitized for public GitHub publication. Sensitive identifiers, credentials, infrastructure values, and client-specific evidence are replaced with clear placeholders.

🧭 Quick Navigation

Tip

For a fast review, start with the Executive Summary and Impact sections. For technical depth, continue into Technical Analysis and Remediation.

🏷️ Title

CVE-2026-45659 - Microsoft SharePoint Deserialization RCE


🧾 Executive Summary

ثغرة أمنية في Microsoft SharePoint Server 2019/2022 و Subscription Edition تسمح لمستخدم مُصادق بصلاحيات منخفضة (Site Member) بتنفيذ أوامر عشوائية على الخادم (RCE). تستغل الثغرة آلية إلغاء التسلسل غير الآمنة (Unsafe Deserialization) في معالج LosFormatter.Deserialize داخل مكتبة Microsoft.SharePoint.Library.

Attribute Value
Identifier CVE-2026-45659
CVSS / Severity 8.8
Weakness Class CWE-502 (Deserialization of Untrusted Data)
Affected Scope المنتج

🔬 Technical Analysis

The weakness was assessed from an application-security and infrastructure-risk perspective. The core issue is classified as Remote Code Execution and was documented in a sanitized form suitable for public portfolio publication.

العنصر التفاصيل
CVE CVE-2026-45659
CVSS 8.8 (High)
النوع Deserialization RCE
المعيار CWE-502 (Deserialization of Untrusted Data)
الصلاحية المطلوبة Site Member (مستخدم عادي)
المنتج Microsoft SharePoint Server

📊 Impact

  • Unauthorized command execution within the affected application context.
  • Potential service takeover, data exposure, and lateral movement depending on deployment privileges.

🛠️ Remediation

  1. تطبيق تحديث مايو 2026 من Microsoft
  2. تقييد صلاحيات المستخدمين إلى الحد الأدنى
  3. مراقبة استدعاءات SPListItem.Update() غير الطبيعية
  4. تفعيل Advanced Threat Protection في SharePoint

🧠 Lessons Learned & Mitigation Strategy

  • Treat every integration boundary as untrusted, especially when application logic forwards user-controlled values to filesystems, shells, parsers, or external tools.
  • Security reviews should validate the complete exploit chain, not only the first vulnerable endpoint; low-severity misconfigurations can become critical when chained.
  • Public-facing documentation should describe risk, root cause, and remediation without exposing operational identifiers, credentials, or reusable exploitation artifacts.
  • Defensive controls should combine preventive validation, runtime least privilege, telemetry, and patch governance to reduce both exploitability and blast radius.

🧼 Publication Sanitization Notes

  • Sensitive infrastructure identifiers, IP addresses, hostnames, credentials, hashes, and e-mail addresses were replaced with explicit placeholders.
  • Reusable operational evidence was minimized or abstracted to keep the document suitable for public GitHub publication.
  • The document uses a consultant-style structure aligned with common web security testing report practices such as OWASP WSTG reporting expectations.

Prepared as a professional cybersecurity portfolio report
Focused on clear risk communication, practical remediation, and defensive improvement.

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Professional vulnerability assessment report for SharePoint deserialization risk, including executive summary, technical impact, remediation, and mitigation strategy.

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