CVE-2026-67631 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 categorized as a heap-based buffer overflow. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the heap segment of computer memory. In the context of database management systems like SQL Server, such vulnerabilities often arise during the processing of complex or malformed queries where input validation is insufficient. The attacker leverages this flaw by crafting specific network packets containing specially formatted data that triggers the overflow condition when processed by the server's query engine. Because heap overflows can corrupt adjacent memory structures, they provide a reliable mechanism for gaining arbitrary code execution privileges on the affected system.
The operational impact of this vulnerability is severe due to its remote nature and the high privilege level typically associated with database administrators or users granted access to sensitive data stores. An authorized attacker who possesses valid credentials to connect to the SQL Server instance can exploit this flaw without requiring physical access to the machine. By sending a maliciously crafted request over the network, the attacker can execute arbitrary code within the security context of the service account running SQL Server. This often results in full system compromise if the database engine is configured with elevated privileges, such as SYSTEM or Administrator rights on Windows environments. The ability to execute code remotely allows for further lateral movement within a corporate network, data exfiltration, installation of backdoors, and disruption of critical business operations dependent on the integrity and availability of the database services.
From a classification perspective, this vulnerability aligns with CWE-122, which denotes heap-based buffer overflow, indicating that the root cause lies in improper boundary checks during memory allocation or copy operations. Furthermore, the exploitation vector maps to MITRE ATT&CK techniques related to remote code execution and privilege escalation. Specifically, it relates to Tactic TA0004 (Privilege Escalation) and Technique T1210 (Exploitation of Remote Services), as well as potentially T1059 (Command and Scripting Interpreter) if the executed payload involves scripting languages commonly used in post-exploitation phases. The presence of this flaw highlights a gap in input sanitization routines within the SQL Server parser or related components responsible for handling incoming network traffic, allowing malicious payloads to bypass standard security controls designed to prevent memory corruption attacks.
Mitigation strategies must focus on immediate patching and rigorous access control measures. Organizations should apply the latest cumulative updates provided by Microsoft that address this specific vulnerability in their SQL Server instances. It is imperative to verify that all affected versions are updated to a supported build where the heap overflow condition has been resolved through improved memory management routines. Additionally, network segmentation plays a crucial role in limiting exposure; database servers should not be directly exposed to untrusted networks such as the public internet and must reside within secure internal subnets accessible only by authorized application servers or administrative workstations. Implementing strict firewall rules that restrict inbound traffic on SQL Server ports (typically TCP 1433) to known IP addresses further reduces the attack surface. Regular vulnerability scanning and penetration testing should be conducted to identify similar memory corruption issues before they can be exploited in production environments, ensuring a proactive defense posture against sophisticated attackers targeting database infrastructure.