CVE-2026-67380 in SQL Server
Summary
by MITRE • 09/08/2026
Heap-based buffer overflow in SQL Server allows an authorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/08/2026
The vulnerability described constitutes a critical security flaw within Microsoft SQL Server, specifically manifesting as a heap-based buffer overflow condition that can be exploited remotely by authenticated users. This type of vulnerability arises when the application writes more data to a block of memory allocated on the heap than it is intended to hold, leading to adjacent memory being overwritten with potentially malicious content. In the context of database management systems like SQL Server, such flaws are particularly dangerous because they often reside in components responsible for parsing and processing complex query structures or handling large datasets. The exploitation vector requires network access, meaning an attacker does not need physical proximity to the server but can target it over a local area network or even across the internet if exposed services are present.
The technical mechanism behind this heap-based buffer overflow typically involves improper bounds checking during memory allocation and data copying operations. When SQL Server processes specific inputs, such as malformed queries, large result sets, or specially crafted binary objects, it may allocate a fixed-size buffer on the heap to store incoming data. If the input exceeds the expected size without adequate validation, the excess data spills over into neighboring memory regions. This overflow can corrupt internal structures used by the database engine, including function pointers, object headers, or control flow mechanisms. By carefully crafting the payload, an attacker can manipulate these overwritten values to redirect execution flow toward shellcode injected within the buffer itself or via other means in the process address space.
The operational impact of successfully exploiting this vulnerability is severe, potentially resulting in complete system compromise. Since SQL Server often runs with elevated privileges on the host operating system, gaining code execution through a heap overflow typically grants the attacker equivalent access rights to those of the database service account. This level of access allows for arbitrary command execution, enabling the installation of backdoors, extraction or modification of sensitive data stored within the databases, and lateral movement across the network infrastructure. Furthermore, because SQL Server is frequently central to enterprise operations, compromising it can lead to significant business disruption, loss of integrity in critical records, and potential regulatory violations regarding data protection standards such as GDPR or HIPAA if personal health information or personally identifiable information is exfiltrated.
From a classification perspective, this vulnerability aligns with CWE-120: Buffer Copy without Checking Size of Input (Classic Buffer Overflow), specifically the heap variant which presents challenges in exploitation due to dynamic memory allocation patterns and potential mitigations like Address Space Layout Randomization (ASLR). In terms of offensive security frameworks, it maps directly to MITRE ATT&CK technique T1203.2: Exploitation for Client Execution via Web Browser or Application Services, although the specific vector here is service-based rather than browser-based. It also relates to privilege escalation paths if the initial foothold provides limited access and the overflow allows elevation to higher system privileges.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary defense is the timely application of vendor-provided security patches that address the specific memory handling flaws within SQL Server binaries. Organizations should prioritize patching based on risk assessments, especially for instances exposed to untrusted networks or those containing high-value data. Additionally, implementing network segmentation can limit exposure by restricting access to database ports from only trusted subnets and authorized application servers. Deploying Intrusion Detection Systems (IDS) with signatures capable of detecting buffer overflow attempts may provide an additional layer of defense in depth, although such measures are not substitutes for patch management. Regular vulnerability scanning and penetration testing should also be conducted to identify similar weaknesses before they can be exploited by malicious actors seeking unauthorized access or data theft.