CVE-2020-1576 in SharePoint Server
Summary
by MITRE
<p>A remote code execution vulnerability exists in Microsoft SharePoint when the software fails to check the source markup of an application package. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the SharePoint application pool and the SharePoint server farm account.</p> <p>Exploitation of this vulnerability requires that a user uploads a specially crafted SharePoint application package to an affected version of SharePoint.</p> <p>The security update addresses the vulnerability by correcting how SharePoint checks the source markup of application packages.</p>
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Analysis
by VulDB Data Team • 02/24/2026
This vulnerability represents a critical remote code execution flaw in Microsoft SharePoint systems that stems from insufficient validation of application package markup sources. The vulnerability resides in the application package processing logic where SharePoint fails to properly verify the integrity and origin of markup content within packaged applications. Attackers can exploit this weakness by uploading maliciously crafted SharePoint application packages that contain malicious code designed to execute within the SharePoint application pool context and potentially escalate privileges to the SharePoint server farm account level.
The technical exploitation requires a specific user interaction pattern where a legitimate user must upload a specially crafted application package to an affected SharePoint instance. This requirement places the vulnerability in the category of user-initiated attacks that leverage social engineering or compromised user credentials to achieve remote code execution. The flaw essentially allows attackers to bypass normal security boundaries by injecting malicious content that gets executed within the SharePoint server environment with elevated privileges.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with access to the SharePoint application pool and server farm account privileges, which typically possess extensive administrative capabilities within the SharePoint environment. This elevated access level enables attackers to potentially extract sensitive data, modify content, establish persistence mechanisms, or pivot to other systems within the network infrastructure. The vulnerability affects SharePoint versions that fail to implement proper source markup validation during application package processing, making it particularly dangerous in enterprise environments where SharePoint serves as a central collaboration platform.
Microsoft addressed this vulnerability through a security update that enhances the markup validation process for application packages, ensuring that SharePoint properly checks the source markup before processing. This remediation aligns with established security principles from the CWE (Common Weakness Enumeration) catalog, specifically addressing CWE-434 which covers "Unrestricted Upload of File with Dangerous Type" and CWE-749 which relates to "Exposed Dangerous Method or Function". Organizations should implement the security update immediately and consider additional mitigations such as restricting user upload permissions, implementing application whitelisting, and monitoring for suspicious file uploads. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreter and T1078 for valid accounts, as attackers would need to leverage legitimate user accounts to upload malicious packages while operating within the SharePoint application context.