CVE-2021-42294 in SharePoint
Summary
by MITRE • 12/15/2021
Microsoft SharePoint Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-42309.
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Analysis
by VulDB Data Team • 12/17/2021
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user-supplied input within the web application framework. This flaw exists in the way SharePoint processes certain HTTP requests and handles specific parameter values, creating an opportunity for attackers to execute arbitrary code on affected systems. The vulnerability stems from a lack of proper input sanitization and validation mechanisms that should normally prevent malicious payloads from being processed within the application's execution context.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious HTTP requests that leverage the insufficient validation controls to inject and execute code within the SharePoint Server environment. This typically involves manipulating specific parameters within web requests to bypass security checks and gain unauthorized access to the underlying system. The flaw allows for arbitrary code execution with the privileges of the SharePoint application pool account, which often runs with elevated permissions on the server. This represents a critical security gap that can be exploited without authentication in many scenarios, making it particularly dangerous for organizations with SharePoint deployments.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete system compromise and data breaches. Attackers can leverage this vulnerability to establish persistent access, escalate privileges, and move laterally within network environments. The vulnerability affects multiple versions of Microsoft SharePoint Server, including SharePoint Server 2016 and SharePoint Server 2019, making it a widespread concern for enterprises that have not yet applied the necessary security patches. Organizations may experience unauthorized data access, system corruption, and potential loss of sensitive information. The vulnerability also creates opportunities for attackers to deploy additional malware or establish backdoors for continued access to the compromised systems.
Microsoft has released security updates to address this vulnerability through the Microsoft Security Response Center, providing patches that correct the input validation issues and strengthen the application's security controls. Organizations should prioritize applying these patches immediately to mitigate the risk of exploitation. Additional mitigations include implementing network segmentation to limit access to SharePoint servers, configuring web application firewalls to monitor and filter suspicious requests, and applying principle of least privilege controls to reduce the impact of potential compromises. This vulnerability aligns with CWE-20, which describes improper input validation, and maps to ATT&CK techniques such as T1059 for command and script injection, and T1078 for valid accounts usage. Security teams should also consider implementing monitoring solutions that can detect anomalous behavior patterns consistent with exploitation attempts, as the vulnerability can be difficult to detect through traditional security controls alone.