Microsoft releases urgent patches for CVE-2026-45659 - dangerous security flaw in SharePoint Server
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In the increasingly complex landscape of enterprise information security, protecting internal storage and collaboration platforms is always a top priority. Recently, Microsoft officially rolled out critical updates to address a high-severity remote code execution (RCE) vulnerability threatening SharePoint Server systems.
How Dangerous is the CVE-2026-45659 Vulnerability?
This security flaw is tracked under the identifier CVE-2026-45659 and has been assigned a severity score of 8.8/10 on the standard CVSS scale. According to reports documented by The Hacker News and Help Net Security, the root cause of this bug lies in the "deserialization of untrusted data."
To put it simply, this flaw occurs when a system accepts external information but lacks adequate security verification, inadvertently treating malicious data sent by attackers as safe internal commands. When the system processes this data, it triggers the hidden malicious code, allowing attackers to take control and execute unauthorized commands on the remote server without requiring any user interaction.
Key characteristics of this vulnerability include:
Low attack complexity: Attackers do not need deep technical expertise or an intimate understanding of the target system's architecture to execute the attack.
Minimal privileges required: The attack does not require high-level administrator privileges. An attacker only needs a standard, authenticated user account on the system - such as Site Member permissions - to successfully exploit it.
High exploitation reliability: Functional testing shows that the malicious payload can operate reliably and consistently achieve the same results across affected components.
Although Microsoft assessed that this vulnerability is "exploitation less likely" in practice, given the relatively easy trigger conditions, proactive patching remains a mandatory priority to mitigate risks.
Why are SharePoint systems always in the crosshairs of cybercriminals?
Cybersecurity experts emphasize that SharePoint servers have always been lucrative targets for cybercriminals and organized international threat groups due to the platform's strategic role in corporate IT infrastructure.
SharePoint serves as a centralized data repository, housing countless sensitive internal documents, project plans, HR information, and critical intellectual property. Furthermore, it is deeply integrated with a wide array of other core Microsoft services, such as Active Directory (the user identity management system), Teams, and Outlook.
This tight integration turns a compromised SharePoint server into an ideal landing pad. From this initial foothold, attackers can perform "lateral movement" - meaning they can leverage the initial breach to infiltrate deeper and spread across the organization's entire network, leading to risks of large-scale data breaches or ransomware extortion.
Affected Versions and Update Solutions
According to technical analysis compiled on Adsecvn, this security issue directly impacts on-premises versions of SharePoint Server deployed within organizations.
To ensure security, system administrators need to immediately check their running versions and upgrade to the following secure, patched builds:
SharePoint Server Subscription Edition: Update to build 16.0.19725.20280 or later.
SharePoint Server 2019: Update to build 16.0.10417.20128 or later.
SharePoint Enterprise Server 2016: Update to build 16.0.5552.1002 or later.
The timely discovery and mitigation of the CVE-2026-45659 vulnerability is an important step by Microsoft to reinforce the security perimeter for enterprises. Faced with potential threats of internal data leakage and systemic lateral attacks, organizations running affected SharePoint Server versions must quickly deploy these updates as soon as possible to protect themselves against cyber threats.
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