UDP Dangerous Database

Port 1434 (MSSQL Browser)

Learn about port 1434 (MSSQL Browser) - security risks, vulnerabilities, and common uses. Find devices with port 1434 open.

Quick Info

Port Number

1434

Protocol

UDP

Service

MSSQL Browser

IANA Name

MSSQL Browser

Service Description

UDP port 1434 is primarily associated with the Microsoft SQL Server Browser service (MSSQL Browser). This service acts as a directory for SQL Server instances running on a given server, particularly named instances or instances running on dynamic ports. When a client application attempts to connect to a SQL Server instance, it first sends a broadcast message to UDP port 1434. The MSSQL Browser service, if running, listens on this port and responds with the instance name, the TCP port number, and the version of the SQL Server instance. This allows the client to then establish a direct connection to the SQL Server instance on the designated TCP port. Historically, this service was essential for discovering SQL Server instances, especially before the prevalence of Active Directory and standardized naming conventions. The protocol is simple: a client sends a 'SQLServerBrowser' string, and the server responds with a string containing instance details separated by semicolons.

## Firewall Recommendations

Whether to allow or block port 1434 depends heavily on the network environment and security posture. If SQL Server instances are primarily accessed within a trusted network and the MSSQL Browser service is essential for client connectivity, allowing the port with strict firewall rules is acceptable. However, if the SQL Server instances are not intended to be publicly accessible or if alternative discovery mechanisms (e.g., static port assignments, DNS records) are in place, blocking UDP port 1434 is recommended. Best practices include: 1. Limit access to port 1434 to only authorized IP addresses or subnets. 2. Ensure the SQL Server Browser service is patched with the latest security updates. 3. Consider disabling the SQL Server Browser service if it's not required for client connectivity, especially in environments where all SQL Server instances use static ports and are well-documented. 4. Implement intrusion detection/prevention systems to monitor for suspicious activity on this port.

Security Information

Port 1434 presents several security risks. Because the MSSQL Browser service provides information about SQL Server instances, it can be used by attackers to enumerate potential targets. This information includes the SQL Server version, which can be used to identify known vulnerabilities. Furthermore, vulnerabilities within the MSSQL Browser service itself can be exploited to gain unauthorized access to the server. The service runs with elevated privileges, so a successful attack could lead to system compromise. Attackers often target this port to map out SQL Server deployments within a network, identify vulnerable versions, and potentially launch attacks against the SQL Server instances themselves.

Known Vulnerabilities

CVE	Name	Severity	Description
CVE-2000-1209	SQL Server Resolution Service Buffer Overflow	High	Buffer overflow in SQL Server Resolution Service (MSSQL Browser) could allow remote attackers to execute arbitrary code.
CVE-2012-1823	SQL Server Browser Service Information Disclosure Vulnerability	Medium	The SQL Server Browser Service in Microsoft SQL Server 2005 SP4, 2008 SP2 and SP3, and 2008 R2 SP1 and SP2 allows remote attackers to obtain sensitive information from process memory via a crafted request, aka "SQL Server Browser Service Information Disclosure Vulnerability." This CVE is related to information disclosure.
CVE-2002-0367	Possible buffer overflow in Microsoft SQL Server	Medium	A vulnerability exists in Microsoft SQL Server that can be exploited by a buffer overflow attack. A remote attacker could send a specially crafted packet that overflows a buffer and possibly allows for execution of arbitrary code.
CVE-2018-0802	Microsoft SQL Server Remote Code Execution Vulnerability	Critical	A remote code execution vulnerability exists in Microsoft SQL Server Reporting Services when it incorrectly handles page navigation. An attacker who successfully exploited this vulnerability could execute code in the context of the Reporting Services service account. To exploit the vulnerability, an authenticated attacker would need to upload a specially crafted file to the server.