CVE-2002-0109 in BEFN2PS4
Summary
by MITRE
Linksys EtherFast BEFN2PS4, BEFSR41, and BEFSR81 Routers, and possibly other products, allow remote attackers to gain sensitive information and cause a denial of service via an SNMP query for the default community string "public," which causes the router to change its configuration and send SNMP trap information back to the system that initiated the query.
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Analysis
by VulDB Data Team • 06/27/2021
This vulnerability affects Linksys EtherFast series routers including models BEFN2PS4, BEFSR41, and BEFSR81, along with potentially other similar devices. The flaw resides in the routers' SNMP implementation where the default community string "public" is improperly handled. When an unauthorized remote attacker sends an SNMP query using this default community string, the router undergoes a configuration change that exposes sensitive information and simultaneously generates SNMP trap messages directed back to the initiating system. This represents a critical security weakness that combines information disclosure with potential denial of service capabilities.
The technical implementation of this vulnerability demonstrates poor access control mechanisms within the router's SNMP service. The default community string "public" should never provide administrative access or trigger configuration changes, yet this implementation allows such behavior. The router's response to the SNMP query results in a configuration modification that inadvertently exposes internal system information through SNMP traps. This configuration change can include sensitive data such as router configuration parameters, network settings, or other system information that should remain protected from unauthorized access. The vulnerability creates a situation where an attacker can both gather intelligence about the network infrastructure and potentially disrupt normal operations through the denial of service component.
From an operational perspective, this vulnerability creates a significant risk for network administrators who may not be aware that their routers are vulnerable to remote exploitation. The attack requires only basic SNMP knowledge and can be executed from any location with network access to the router. The exposure of configuration information through SNMP traps provides attackers with valuable intelligence for planning further attacks against the network infrastructure. The denial of service aspect means that legitimate network operations could be disrupted, potentially affecting business continuity. This vulnerability particularly impacts small to medium businesses that may rely on consumer-grade networking equipment without proper security hardening or monitoring in place.
The vulnerability maps directly to CWE-255: Credentials Management Errors and CWE-310: Cryptographic Issues within the Common Weakness Enumeration framework. It also aligns with ATT&CK technique T1046: Network Service Scanning and T1071.004: Application Layer Protocol: DNS to demonstrate how an attacker can leverage basic network services to gain unauthorized access. Organizations should implement immediate mitigations including disabling SNMP if not required, changing default community strings to complex, non-default values, and implementing network segmentation to limit access to these devices. Additionally, regular security assessments should be conducted to identify and remediate similar vulnerabilities in network infrastructure equipment. The incident highlights the critical importance of proper configuration management and the dangers of leaving default settings unchanged in network devices.