CVE-2021-34517 in SharePoint Server
Summary
by MITRE • 07/15/2021
Microsoft SharePoint Server Spoofing Vulnerability
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Analysis
by VulDB Data Team • 07/17/2021
The CVE-2021-34517 vulnerability represents a critical spoofing flaw in Microsoft SharePoint Server that allows attackers to manipulate user interfaces and deceive users into believing they are interacting with legitimate SharePoint components. This vulnerability specifically affects SharePoint Server 2016 and SharePoint Server 2019 installations, creating a significant risk for organizations relying on these platforms for document management and collaboration. The flaw stems from improper validation of user interface elements within the SharePoint framework, enabling malicious actors to craft deceptive web pages that mimic legitimate SharePoint interfaces with alarming accuracy.
The technical implementation of this vulnerability exploits the way SharePoint Server handles user authentication prompts and interface rendering. Attackers can leverage this weakness to create convincing phishing pages that trick users into entering credentials or sensitive information. The vulnerability operates by manipulating the SharePoint Server's ability to properly validate and display user interface elements, particularly during authentication processes. This allows threat actors to present false login screens or administrative interfaces that appear genuine to unsuspecting users. The flaw essentially bypasses normal security checks that should verify the legitimacy of interface components, creating a trust relationship that can be exploited for credential theft or further system compromise.
From an operational impact perspective, organizations running affected SharePoint Server versions face substantial risks including unauthorized access to sensitive documents, potential data breaches, and compromised user credentials. The vulnerability can be exploited through various attack vectors including malicious email attachments, compromised websites, or social engineering campaigns that direct users to specially crafted SharePoint pages. Security teams must consider the potential for widespread impact across enterprise environments where SharePoint serves as a central collaboration platform. The spoofing capability extends beyond simple credential theft to potentially enable more sophisticated attacks such as privilege escalation or lateral movement within networks. Organizations may experience cascading effects as compromised credentials can lead to access to additional systems and data repositories.
Mitigation strategies for CVE-2021-34517 should prioritize immediate patch deployment from Microsoft as the primary defense mechanism. Organizations must ensure all SharePoint Server 2016 and 2019 installations receive the relevant security updates released by Microsoft to address this specific spoofing vulnerability. Network segmentation and monitoring solutions should be implemented to detect anomalous behavior patterns that might indicate exploitation attempts. Security awareness training programs should emphasize the importance of verifying interface legitimacy and recognizing potential spoofing attempts. Implementing multi-factor authentication across SharePoint environments adds an additional layer of protection even if credential theft occurs. The vulnerability aligns with CWE-601 and ATT&CK techniques related to client-side attacks and credential harvesting, making it particularly concerning for organizations following industry security standards and frameworks. Regular security assessments should include verification of SharePoint Server configurations to ensure proper interface validation and authentication controls remain effective.