CVE-2021-41344 in SharePoint Server
Summary
by MITRE • 10/13/2021
Microsoft SharePoint Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-40487.
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Analysis
by VulDB Data Team • 10/15/2021
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user input within the web application's processing pipeline. This flaw exists in the way SharePoint handles certain HTTP requests and parameter parsing operations, creating an opportunity for malicious actors to execute arbitrary code on affected systems. The vulnerability stems from insufficient sanitization of input parameters that are processed through the server's web interface, allowing attackers to inject malicious payloads that can be interpreted and executed by the underlying application server. The issue specifically affects SharePoint Server versions prior to the security updates released in October 2021, with the vulnerability being classified under CWE-20 as improper input validation. Attackers can exploit this weakness by crafting specially malformed requests that bypass normal authentication mechanisms and directly target the vulnerable processing functions. The remote code execution capability enables threat actors to gain full control over affected SharePoint servers, potentially leading to data breaches, lateral movement within network environments, and establishment of persistent backdoors. This vulnerability aligns with ATT&CK technique T1190 for exploitation of remote services and T1059 for execution through command and scripting interpreter, making it particularly dangerous in enterprise environments where SharePoint servers often serve as critical collaboration platforms. The flaw is particularly concerning because SharePoint servers frequently host sensitive corporate data and are often accessible from external networks, making them attractive targets for attackers seeking to establish initial access points. Organizations running unpatched SharePoint Server installations face significant risk of compromise, as the vulnerability can be exploited without requiring prior authentication or specialized knowledge of the target environment.
The technical exploitation of CVE-2021-41344 relies on the server's failure to properly validate and sanitize input parameters that flow through the application's request processing chain. When SharePoint receives HTTP requests containing crafted parameters, the application fails to adequately filter or escape these inputs before processing them within the server-side execution context. This allows attackers to inject malicious code sequences that are subsequently executed by the SharePoint server's processing engine. The vulnerability manifests when specific request parameters are manipulated to trigger a code path that does not properly validate user-supplied data, creating a direct execution channel for attacker-controlled payloads. The exploitation process typically involves sending HTTP requests with specially crafted payloads that leverage the application's trust in certain input formats, bypassing standard security controls and access restrictions. This vulnerability is particularly dangerous because it operates at the application layer and can be exploited through standard web protocols, making it accessible to attackers with basic web exploitation knowledge. The affected SharePoint Server versions include those from the 2016 and 2019 releases, with the vulnerability being present in multiple components of the SharePoint infrastructure including the web application framework and content processing modules. The flaw creates a persistent threat vector that can be leveraged for various attack objectives, including data exfiltration, system compromise, and establishment of command and control channels. Security researchers have noted that this vulnerability can be chained with other exploits to extend attack capabilities and achieve broader system compromise.
Organizations affected by CVE-2021-41344 face severe operational consequences that extend beyond immediate system compromise. The remote code execution capability allows attackers to fully compromise SharePoint servers and potentially gain access to sensitive corporate data stored within these platforms. This vulnerability enables threat actors to perform reconnaissance activities, escalate privileges, and establish persistent access to enterprise networks through compromised SharePoint installations. The impact is particularly significant for organizations that rely heavily on SharePoint for document management, collaboration, and enterprise content services, as these systems often contain confidential business information, intellectual property, and personally identifiable data. The vulnerability's exploitation can lead to substantial financial losses through data breaches, regulatory fines, and operational disruption. Additionally, compromised SharePoint servers can serve as launch points for lateral movement attacks, allowing attackers to explore and target other systems within the network perimeter. Organizations may experience service degradation or complete outages if attackers choose to deploy destructive payloads or ransomware through the compromised SharePoint infrastructure. The vulnerability's presence in widely deployed SharePoint Server versions means that many enterprises are potentially exposed, with the risk being particularly high for organizations that have not implemented proper patch management processes. The exploitation of this vulnerability can also result in compliance violations under data protection regulations such as gdpr, hipaa, and other industry-specific standards that require robust security controls and incident response capabilities.
Mitigation strategies for CVE-2021-41344 should prioritize immediate implementation of Microsoft security updates and patches released in October 2021. Organizations must ensure that all SharePoint Server installations are updated to the latest security patches, as these updates contain the necessary fixes to address the input validation flaws that enable remote code execution. Network segmentation and access controls should be implemented to limit exposure of SharePoint servers to untrusted networks, reducing the attack surface available to potential threat actors. Regular monitoring of web application logs and network traffic should be established to detect anomalous activities that may indicate exploitation attempts, with security information and event management systems configured to alert on suspicious request patterns. Organizations should implement web application firewalls and intrusion detection systems specifically configured to identify and block malicious payloads targeting SharePoint vulnerabilities. The principle of least privilege should be enforced by restricting administrative access to SharePoint servers and implementing multi-factor authentication for all administrative accounts. Regular vulnerability assessments and penetration testing should be conducted to identify and remediate similar input validation issues within the broader SharePoint infrastructure. Security teams should also establish incident response procedures specifically designed to address SharePoint server compromises, including forensic analysis capabilities and recovery protocols. Additionally, organizations should consider implementing application whitelisting policies to restrict execution of unauthorized code on SharePoint servers, and maintain regular backups of SharePoint content to facilitate recovery in case of successful exploitation. The implementation of these mitigations should be prioritized based on the criticality of the SharePoint servers within the organization's infrastructure and the sensitivity of the data they contain.