CVE-2026-26115 is a vulnerability identified in Microsoft SQL Server 2016 Service Pack 3 (GDR), specifically version 13.0.0, involving improper validation of the specified type of input (CWE-1287). This flaw allows an attacker who is already authorized to access the SQL Server over the network to escalate their privileges. The vulnerability arises because the server does not correctly validate the type of input it receives, which can be exploited to bypass security controls and gain elevated privileges. The CVSS v3.1 base score is 8.8, reflecting a high severity due to the network attack vector (AV:N), low attack complexity (AC:L), and the requirement of privileges (PR:L) but no user interaction (UI:N). The vulnerability affects confidentiality, integrity, and availability (all rated high), meaning an attacker could potentially access sensitive data, modify or delete data, or disrupt database services. The scope remains unchanged (S:U), indicating the impact is limited to the vulnerable component. No known exploits have been reported in the wild yet, but the vulnerability is publicly disclosed and assigned a CVE ID, indicating the need for immediate attention. The lack of available patches at the time of reporting necessitates interim mitigations to reduce risk.

The vulnerability allows an authorized attacker to elevate privileges on Microsoft SQL Server 2016 SP3 instances remotely, potentially leading to full control over the database server. This can result in unauthorized access to sensitive data, unauthorized data modification or deletion, and disruption of database availability. Organizations relying on SQL Server 2016 SP3 for critical applications, including financial services, healthcare, government, and large enterprises, face significant risk of data breaches and operational disruption. The elevated privileges could also facilitate lateral movement within networks, increasing the overall risk posture. Given the widespread use of Microsoft SQL Server in enterprise environments worldwide, the impact could be extensive if exploited at scale. The absence of known exploits currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits following public disclosure.

1. Apply official patches from Microsoft as soon as they become available for SQL Server 2016 SP3 to remediate the vulnerability. 2. Until patches are released, restrict network access to SQL Server instances by implementing strict firewall rules and network segmentation, limiting access to only trusted hosts and administrators. 3. Enforce the principle of least privilege for all SQL Server accounts, ensuring users have only the minimum permissions necessary. 4. Monitor SQL Server logs and network traffic for unusual privilege escalation attempts or anomalous behavior indicative of exploitation attempts. 5. Use SQL Server's built-in security features such as Transparent Data Encryption (TDE) and auditing to detect and prevent unauthorized data access or modifications. 6. Regularly review and update security policies and incident response plans to include scenarios involving privilege escalation vulnerabilities. 7. Educate database administrators and security teams about this vulnerability and recommended mitigations to ensure rapid response.