CVE-2024-49064 is a medium-severity vulnerability classified under CWE-611, which pertains to Improper Restriction of XML External Entity (XXE) Reference. This vulnerability affects Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The issue arises because the SharePoint server improperly processes XML input, allowing an attacker to craft malicious XML payloads that include external entity references. When processed by the vulnerable SharePoint server, these external entities can be resolved, potentially leading to unauthorized disclosure of sensitive information. The vulnerability is remotely exploitable over the network (AV:N), requires no privileges (PR:N), but does require user interaction (UI:R), such as clicking a malicious link or submitting crafted XML data. The scope is unchanged (S:U), meaning the vulnerability affects resources within the same security scope. The impact is primarily on confidentiality (C:H), with no impact on integrity or availability. There are no known exploits in the wild at the time of publication, and no official patches have been linked yet. The vulnerability was reserved in October 2024 and published in December 2024, indicating recent discovery and disclosure. The CVSS 3.1 score of 6.5 reflects a medium severity level, balancing the high confidentiality impact against the need for user interaction and the lack of privilege requirements.

For European organizations, this vulnerability poses a significant risk to the confidentiality of sensitive data managed within SharePoint Enterprise Server 2016 environments. SharePoint is widely used across various sectors including government, finance, healthcare, and enterprise businesses in Europe for document management and collaboration. Exploitation could lead to unauthorized disclosure of confidential documents, intellectual property, or personal data, potentially violating GDPR and other data protection regulations. The requirement for user interaction somewhat limits the attack vector but does not eliminate risk, especially in environments where users may be targeted via phishing or social engineering campaigns. The lack of integrity and availability impact means the threat is less about disruption and more about data leakage, which can still have severe reputational and regulatory consequences for European entities.

European organizations should prioritize the following mitigations: 1) Monitor for official Microsoft security advisories and apply patches immediately once available, as no patch links are currently provided. 2) Implement strict input validation and XML parsing configurations to disable external entity processing where possible within SharePoint or related XML processing components. 3) Employ network-level protections such as Web Application Firewalls (WAFs) configured to detect and block malicious XML payloads or unusual external entity references. 4) Conduct user awareness training to reduce the risk of successful social engineering or phishing attempts that could trigger the vulnerability. 5) Review and restrict permissions and access controls on SharePoint to minimize exposure. 6) Use logging and monitoring to detect anomalous XML processing or unexpected outbound network requests that could indicate exploitation attempts. These steps go beyond generic advice by focusing on configuration hardening, user behavior, and proactive detection tailored to the nature of this XXE vulnerability.