TCP Web

Port 8081 (HTTP Proxy Alt)

Learn about port 8081 (HTTP Proxy Alt) - security risks, vulnerabilities, and common uses. Find devices with port 8081 open.

Quick Info

Port Number

8081

Protocol

TCP

Service

HTTP Proxy Alt

IANA Name

HTTP Proxy Alt

Service Description

TCP port 8081 is commonly associated with the HTTP Proxy Alt service. It serves as an alternative port to the standard HTTP port 80, and is often used when port 80 is already in use, blocked by a firewall, or for load balancing purposes. The service operates using the Hypertext Transfer Protocol (HTTP), enabling communication between clients (e.g., web browsers) and servers. When a client is configured to use an HTTP proxy on port 8081, all HTTP requests are directed to the proxy server. The proxy server then forwards these requests to the destination server and relays the response back to the client. This allows for functionalities like content filtering, caching, and anonymity. The use of port 8081, like port 80, does not inherently imply encryption; communication occurs in plaintext unless HTTPS (HTTP over TLS/SSL) is implemented. Its history is tied to the evolution of proxy servers and the need to accommodate various network configurations.

## Firewall Recommendations

Generally, blocking port 8081 is recommended unless it is specifically needed for a legitimate HTTP proxy service. If the port must be open, implement strong authentication and authorization controls to restrict access to authorized users only. Enforce HTTPS (TLS/SSL) to encrypt communication and protect sensitive data. Regularly update the proxy server software to patch security vulnerabilities. Consider implementing intrusion detection and prevention systems (IDS/IPS) to monitor traffic on port 8081 and detect malicious activity. Rate limiting can also help mitigate the impact of DDoS attacks. If the proxy is only needed for internal use, restrict access to it from the external network using firewall rules. Logging and monitoring of proxy server activity are crucial for detecting and responding to security incidents.

Security Information

Exposing an HTTP proxy on port 8081 without proper authentication and authorization controls can create significant security risks. If the proxy is configured as an open proxy, it can be exploited by malicious actors to mask their IP addresses, bypass security restrictions, and launch attacks such as DDoS, spam campaigns, and port scanning. Furthermore, if the proxy server is vulnerable to exploits like HTTP request smuggling or response splitting, attackers can leverage it to compromise internal systems or redirect users to malicious websites. Unencrypted communication over HTTP also exposes sensitive data transmitted through the proxy to interception and eavesdropping. The port is targeted because it is frequently misconfigured or left with default credentials, making it an easy entry point for attackers seeking to exploit vulnerable systems or networks.

Known Vulnerabilities

CVE	Name	Severity	Description
CVE-2019-9511	HTTP/2 Denial of Service (DoS)	High	An attacker can cause excessive resource consumption in servers supporting HTTP/2 due to the processing of malformed frames, leading to a denial of service.
CVE-2019-9513	HTTP/2 RESET Flood	High	An attacker can send a high rate of HTTP/2 RESET frames to a server, causing excessive resource consumption and potentially leading to a denial of service.
CVE-2016-2107	OpenSSL Padding Oracle Vulnerability	Medium	The OpenSSL padding oracle vulnerability (Lucky 13) can allow an attacker to decrypt traffic if the proxy uses a vulnerable version of OpenSSL to handle HTTPS connections.