CVE-2003-0496 in SQL Server
Summary
by MITRE
Microsoft SQL Server before Windows 2000 SP4 allows local users to gain privileges as the SQL Server user by calling the xp_fileexist extended stored procedure with a named pipe as an argument instead of a normal file.
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Analysis
by VulDB Data Team • 02/15/2025
This vulnerability exists in Microsoft SQL Server versions prior to Windows 2000 Service Pack 4 and represents a privilege escalation flaw that allows local attackers to execute code with elevated privileges. The vulnerability stems from how the xp_fileexist extended stored procedure processes input arguments, specifically when a named pipe is passed instead of a conventional file path. This behavior creates a security boundary violation where the system incorrectly interprets named pipe operations as file system operations, enabling unauthorized privilege elevation.
The technical flaw manifests in the improper handling of file system operations within SQL Server's extended stored procedures. When the xp_fileexist procedure receives a named pipe as input, the underlying Windows kernel APIs fail to properly validate the argument type, causing the system to treat the pipe as if it were a regular file. This misinterpretation occurs because the procedure does not adequately distinguish between file paths and named pipe identifiers, allowing attackers to leverage this ambiguity for privilege escalation. The vulnerability is classified under CWE-20, which deals with improper input validation, and specifically relates to CWE-78, improper neutralization of special elements used in OS commands.
The operational impact of this vulnerability is significant as it enables local users to gain elevated privileges without requiring authentication or remote access. Attackers can exploit this flaw to execute arbitrary code with the privileges of the SQL Server service account, which typically runs with elevated system permissions. This privilege escalation allows for complete system compromise, data exfiltration, and potential lateral movement within the network. The vulnerability is particularly dangerous because it does not require network connectivity or specialized tools beyond basic SQL Server access, making it a prime target for attackers seeking persistent access to database servers.
From an adversary perspective, this vulnerability aligns with ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges to escalate access. The attack chain typically begins with a local user gaining access to SQL Server, followed by the exploitation of the xp_fileexist procedure to escalate privileges. The vulnerability also maps to ATT&CK technique T1059, where adversaries use command-line interfaces to execute malicious code, as the named pipe manipulation can trigger command execution. Security professionals should note that this vulnerability affects systems where SQL Server runs with elevated privileges, particularly in enterprise environments where database servers are often configured with administrative rights.
Mitigation strategies should focus on applying the Microsoft Windows 2000 Service Pack 4 update, which addresses the underlying validation issue in the xp_fileexist procedure. Organizations should also implement least privilege principles by ensuring SQL Server services run with minimal required permissions rather than administrative accounts. Additional defensive measures include disabling unnecessary extended stored procedures, implementing proper network segmentation, and monitoring for unusual SQL Server activity patterns. The vulnerability serves as a reminder of the importance of proper input validation in database systems and demonstrates how seemingly minor implementation flaws can result in significant security implications. Regular security assessments and patch management processes are essential to prevent exploitation of similar vulnerabilities in other database systems and applications.