TCP Dangerous Database

Port 1521 (Oracle)

Learn about port 1521 (Oracle) - security risks, vulnerabilities, and common uses. Find devices with port 1521 open.

Quick Info

Port Number

1521

Protocol

TCP

Service

Oracle

IANA Name

Oracle

Service Description

TCP port 1521 is the default listening port for the Oracle Database Listener. The Oracle Listener acts as a network traffic director for the Oracle database, receiving incoming client connection requests and routing them to the appropriate database instance. When a client application attempts to connect to an Oracle database, it first connects to the Listener on port 1521. The Listener then authenticates the client (if authentication is configured) and determines the appropriate database instance to handle the connection. Once determined, the Listener establishes a dedicated connection between the client and the database instance, often using a different port (though it can reuse the same port). This process is fundamental to Oracle's client-server architecture. The Listener uses the Oracle Net Services protocol, which supports various transport protocols including TCP/IP. The actual communication between the client and the database instance uses a proprietary protocol called Two-Task Common (TTC), which is encapsulated within the TCP connection.

## Firewall Recommendations

Ideally, port 1521 should only be accessible from trusted networks or specific client machines. Implement strict firewall rules to limit access to only authorized IP addresses or subnets. Consider using a VPN for remote access to the database. Regularly audit and patch the Oracle Listener to address known vulnerabilities. Enforce strong authentication for the Listener and the database itself. Monitor the Listener logs for suspicious activity. If the database and client applications are on the same network segment, consider blocking external access to port 1521 entirely. If external access is absolutely required, use a web application firewall (WAF) or intrusion detection/prevention system (IDS/IPS) to monitor and filter traffic on port 1521.

Security Information

Port 1521 is a prime target for attackers because it represents the entry point to an Oracle database, which typically contains sensitive data. Common attack vectors include exploiting vulnerabilities in the Oracle Listener itself, attempting to brute-force database credentials, exploiting SQL injection vulnerabilities in applications communicating with the database, and attempting to gain unauthorized access through misconfigured Listener settings. A poorly configured Listener can be exploited to perform denial-of-service (DoS) attacks, gain unauthorized access to the database, or even execute arbitrary code on the server. The Listener can also be targeted to perform Listener poisoning attacks, where an attacker registers a malicious service with the Listener, redirecting legitimate client connections to a rogue database server.

Known Vulnerabilities

CVE	Name	Severity	Description
CVE-2012-1675	Oracle Database Listener Password Disclosure Vulnerability	High	This vulnerability allows remote attackers to obtain sensitive information (passwords) via a TNS listener poisoning attack.
CVE-2012-3150	Oracle Database Listener Remote Code Execution Vulnerability	Critical	This vulnerability allows remote attackers to execute arbitrary code via a crafted TNS packet.
CVE-2014-6578	Oracle Database Listener Denial of Service Vulnerability	Medium	This vulnerability allows remote attackers to cause a denial of service (crash) via a crafted TNS packet.
CVE-2023-21837	Oracle Database SQL Developer vulnerability	High	A vulnerability within SQL Developer could allow an attacker to gain unauthorized access to the system.