CVE-2026-94512: SQL Server RCE Vulnerability

CVE-2026-94512 Overview

CVE-2026-94512 is a heap-based buffer overflow vulnerability in Microsoft SQL Server. An authenticated attacker can exploit the flaw over a network to execute arbitrary code within the context of the SQL Server process. The weakness is tracked under CWE-122: Heap-based Buffer Overflow.

Microsoft published the advisory through the Microsoft Security Response Center (MSRC) update guide. Exploitation requires low-privilege authenticated access, no user interaction, and low attack complexity, making SQL Server deployments with broad network reachability particularly exposed.

Critical Impact

An authenticated attacker with network access to a vulnerable SQL Server instance can corrupt heap memory and execute code with the privileges of the database service, risking full database compromise and lateral movement.

Affected Products

• Microsoft SQL Server (specific build numbers listed in the MSRC advisory)
• SQL Server instances reachable over the network from authenticated client contexts
• Deployments where database engine services run with elevated service accounts

Discovery Timeline

• 2026-10-13 - CVE CVE-2026-94512 published to NVD
• 2026-10-13 - Last updated in NVD database

Technical Details for CVE-2026-94512

Vulnerability Analysis

The vulnerability is a heap-based buffer overflow inside the SQL Server database engine. An attacker who holds valid credentials can send crafted input that causes the server to write past the bounds of a heap-allocated buffer. The overflow corrupts adjacent heap metadata or object pointers, which an attacker can leverage to redirect execution.

Because SQL Server typically runs under a dedicated service account with access to database files, backups, and linked servers, successful code execution can expose stored data, credentials, and connected systems. Confidentiality, integrity, and availability are all impacted.

Root Cause

Heap-based buffer overflows [CWE-122] occur when code allocates memory on the heap and later writes more data into the buffer than it can hold. In this case, a request-handling path in SQL Server fails to validate the size of attacker-controlled input before copying it into a heap region. Microsoft has not published root-cause internals beyond the MSRC advisory.

Attack Vector

The attack vector is network-based and requires authentication. An attacker with a low-privileged database login can establish a connection to the SQL Server instance and submit a malformed query, parameter, or protocol message that triggers the overflow. User interaction is not required, and the scope remains unchanged, meaning code executes in the SQL Server service context.

No public proof-of-concept exploit, Exploit-DB entry, or CISA Known Exploited Vulnerabilities listing is associated with this CVE at the time of publication. Technical details beyond the advisory are not disclosed. Refer to the Microsoft Vulnerability CVE-2026-94512 advisory for vendor guidance.

Detection Methods for CVE-2026-94512

Indicators of Compromise

• Unexpected crashes or restarts of the sqlservr.exe process accompanied by Windows Error Reporting (WER) dumps referencing access violations in heap routines.
• SQL Server error log entries showing stack dumps, mini-dump creation, or Non-yielding Scheduler and memory corruption messages near the time of suspicious logins.
• Successful authentications from unexpected source IPs followed immediately by abnormal query patterns or malformed protocol traffic on TCP/1433.

Detection Strategies

• Monitor SQL Server for process crashes correlated with recent client connections and investigate accompanying memory dumps for heap corruption signatures.
• Alert on new or unusual child processes spawned by sqlservr.exe, such as cmd.exe, powershell.exe, or rundll32.exe, which indicate post-exploitation activity.
• Baseline authenticated SQL traffic and flag anomalous Tabular Data Stream (TDS) payload sizes or malformed packets from low-privileged accounts.

Monitoring Recommendations

• Forward SQL Server error logs, Windows Security event logs, and endpoint telemetry to a centralized analytics platform for correlation across database and host layers.
• Enable SQL Server audit for login events and failed logins to detect credential-stuffing or reconnaissance preceding exploitation.
• Track outbound connections from database hosts to detect data staging or command-and-control activity after a successful compromise.

How to Mitigate CVE-2026-94512

Immediate Actions Required

• Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-94512 to all affected SQL Server builds.
• Inventory SQL Server instances, including developer and legacy systems, and prioritize patching for those reachable from untrusted networks.
• Rotate SQL Server service account credentials and review login privileges, removing unnecessary accounts and enforcing least privilege.

Patch Information

Microsoft has released a security update addressing CVE-2026-94512. Administrators should consult the Microsoft Vulnerability CVE-2026-94512 advisory for the specific cumulative update, GDR package, or security-only build corresponding to each supported SQL Server version. Apply updates through standard SQL Server patch workflows and validate database engine availability after installation.

Workarounds

• Restrict network access to SQL Server using host-based firewalls, network ACLs, and private endpoints so only authorized application tiers can reach TCP/1433 and dynamic SQL ports.
• Disable or remove unused SQL logins and enforce strong authentication, including Windows or Entra ID integrated authentication where possible, to reduce the authenticated attack surface.
• Place SQL Server behind a jump host or bastion for administrative access and require multi-factor authentication for all privileged database users.