CVE-2017-0255 in SharePoint Foundation
Summary
by MITRE
Microsoft SharePoint Foundation 2013 SP1 allows an elevation of privilege vulnerability when it does not properly sanitize a specially crafted web request, aka "Microsoft SharePoint XSS Vulnerability".
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Analysis
by VulDB Data Team • 12/22/2020
The vulnerability identified as CVE-2017-0255 represents a critical elevation of privilege flaw within Microsoft SharePoint Foundation 2013 SP1 that stems from insufficient sanitization of web requests. This weakness specifically manifests as a cross-site scripting vulnerability that enables attackers to execute malicious code within the context of a victim's browser session. The vulnerability resides in the SharePoint Foundation's handling of user-supplied input within web requests, where the system fails to adequately validate or sanitize potentially malicious data before processing. According to CWE-79, this vulnerability falls under the category of Cross-Site Scripting, which occurs when an application includes untrusted data in a new web page without proper validation or escaping, allowing attackers to inject client-side scripts into web pages viewed by other users. The impact of this vulnerability extends beyond simple script injection as it provides attackers with the capability to escalate their privileges within the SharePoint environment, potentially gaining unauthorized access to sensitive data, modifying content, or even executing arbitrary commands on the server.
The technical exploitation of this vulnerability requires an attacker to craft a specially designed web request that contains malicious script code within parameters or input fields that SharePoint processes. When SharePoint Foundation 2013 SP1 receives such a request, the insufficient sanitization allows the malicious payload to be executed in the browser context of authenticated users, effectively enabling the attacker to perform actions with the privileges of the targeted user. This particular flaw operates at the application layer and can be leveraged through various attack vectors including email attachments, web forms, or crafted URLs that when clicked by an authenticated user, trigger the malicious script execution. The vulnerability's exploitation aligns with ATT&CK technique T1059.007, which involves the use of script-based attacks, and specifically targets the web application attack surface of SharePoint installations. The flaw essentially creates a persistent threat vector where a single compromised user session can serve as an entry point for broader network infiltration, as the malicious script execution can potentially access additional resources or escalate privileges further within the SharePoint farm.
The operational impact of CVE-2017-0255 extends significantly beyond the immediate scope of a single compromised session, as it provides attackers with the capability to manipulate SharePoint content, access restricted documents, and potentially pivot to other systems within the network. Organizations running SharePoint Foundation 2013 SP1 are particularly vulnerable since this version lacks proper input validation mechanisms that would normally prevent such attacks. The vulnerability can lead to data breaches, content tampering, and unauthorized access to sensitive corporate information stored within SharePoint repositories. Additionally, the privilege escalation capability means that even if an attacker initially gains access through a low-privilege account, they can potentially elevate their access level to administrative privileges within the SharePoint environment. This makes the vulnerability particularly dangerous in enterprise environments where SharePoint serves as a central collaboration platform for business-critical applications and sensitive data storage. The attack surface is further expanded by the fact that SharePoint Foundation 2013 SP1 installations often integrate with other Microsoft products and services, potentially allowing attackers to leverage the compromised SharePoint instance as a stepping stone for broader attacks against Active Directory or other enterprise systems.
Organizations affected by CVE-2017-0255 should implement immediate mitigations including applying the relevant Microsoft security patches and updates that address the XSS vulnerability in SharePoint Foundation 2013 SP1. Microsoft released security bulletin MS17-025 that specifically addresses this vulnerability, and organizations should ensure all SharePoint installations are updated to the latest security patches. Beyond patching, network administrators should consider implementing additional security controls such as web application firewalls that can detect and block malicious requests containing known XSS patterns. Input validation and output encoding should be strengthened across all SharePoint web applications to prevent malicious code from being executed in user contexts. Security monitoring should be enhanced to detect unusual patterns of user activity that might indicate exploitation attempts, including unexpected content modifications or unauthorized access attempts. Organizations should also conduct comprehensive vulnerability assessments to identify all instances of SharePoint Foundation 2013 SP1 within their environment and ensure proper access controls are implemented to limit the potential impact of any successful exploitation. The mitigation strategy should align with security frameworks such as NIST SP 800-53 controls for application security and should include regular security testing to verify that input sanitization mechanisms remain effective against evolving attack techniques. Additionally, user education and awareness programs should be implemented to reduce the risk of social engineering attacks that might exploit this vulnerability through phishing or malicious email attachments.