CVE-2017-6741 in IOS
Summary
by MITRE
The Simple Network Management Protocol (SNMP) subsystem of Cisco IOS 12.0 through 12.4 and 15.0 through 15.6 and IOS XE 2.2 through 3.17 contains multiple vulnerabilities that could allow an authenticated, remote attacker to remotely execute code on an affected system or cause an affected system to reload. An attacker could exploit these vulnerabilities by sending a crafted SNMP packet to an affected system via IPv4 or IPv6. Only traffic directed to an affected system can be used to exploit these vulnerabilities. The vulnerabilities are due to a buffer overflow condition in the SNMP subsystem of the affected software. The vulnerabilities affect all versions of SNMP: Versions 1, 2c, and 3. To exploit these vulnerabilities via SNMP Version 2c or earlier, the attacker must know the SNMP read-only community string for the affected system. To exploit these vulnerabilities via SNMP Version 3, the attacker must have user credentials for the affected system. All devices that have enabled SNMP and have not explicitly excluded the affected MIBs or OIDs should be considered vulnerable. Cisco Bug IDs: CSCve66658.
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Analysis
by VulDB Data Team • 07/31/2025
The vulnerability identified as CVE-2017-6741 represents a critical buffer overflow condition within the Simple Network Management Protocol subsystem of Cisco IOS and IOS XE operating systems. This flaw affects multiple software versions spanning from IOS 12.0 through 12.4 and 15.0 through 15.6, along with IOS XE 2.2 through 3.17, making it a widespread issue across Cisco's network infrastructure products. The vulnerability operates at the protocol level, specifically targeting the SNMP implementation that handles network management communications. The buffer overflow occurs when the system processes specially crafted SNMP packets, creating a potential entry point for malicious actors to gain unauthorized access to network devices. This type of vulnerability falls under CWE-121, which categorizes buffer overflow conditions that can lead to arbitrary code execution or system instability.
The exploitation mechanism requires an authenticated remote attacker who can send malicious SNMP packets to the targeted system through either IPv4 or IPv6 networks. The attack vector is particularly concerning because it allows remote code execution without requiring physical access to the device, making it a significant threat to network security infrastructure. The vulnerability affects all three versions of SNMP - Version 1, 2c, and 3 - demonstrating the comprehensive nature of the flaw across the entire SNMP protocol spectrum. For SNMP Version 2c and earlier versions, attackers must possess the SNMP read-only community string to successfully exploit the vulnerability, which represents a baseline authentication requirement. However, for SNMP Version 3 exploitation, attackers need valid user credentials, indicating that the attack complexity increases with the security level of the SNMP implementation. This distinction aligns with ATT&CK technique T1078 which covers valid accounts as a method for maintaining persistence and access to target systems.
The operational impact of this vulnerability extends beyond simple code execution to include potential system reloads, which can disrupt network services and create availability issues for critical infrastructure. When an affected system experiences a buffer overflow, it can cause the device to crash or restart, leading to denial of service conditions that may affect network monitoring, management, and overall connectivity. The fact that all devices with enabled SNMP and without explicit MIB or OID exclusions are considered vulnerable means that organizations with standard SNMP configurations are at risk. This widespread exposure creates a significant challenge for network administrators who must assess their entire infrastructure for potential exposure. The vulnerability's presence in multiple IOS versions indicates that it was likely introduced early in the software development cycle and persisted across numerous releases, making it a long-standing security issue that required multiple patches and updates to address. Organizations implementing network monitoring and management systems using SNMP protocols would be particularly vulnerable to this type of attack, as these systems often serve as critical infrastructure components that require continuous availability and security.
Mitigation strategies for CVE-2017-6741 should include immediate implementation of Cisco's recommended security patches and updates for affected IOS and IOS XE versions. Network administrators should disable SNMP if it is not required for network operations, or implement strict access controls including SNMP community string management, firewall rules restricting SNMP traffic to authorized management stations, and explicit exclusion of vulnerable MIBs or OIDs. The implementation of network segmentation and monitoring solutions can help detect unauthorized SNMP traffic patterns that might indicate exploitation attempts. Organizations should also consider implementing network access control measures and regular vulnerability assessments to identify and remediate similar issues before they can be exploited. The vulnerability demonstrates the importance of maintaining up-to-date security patches and the critical need for network administrators to understand their network infrastructure's attack surface, particularly in relation to management protocols that provide access to network devices. Regular security audits and network monitoring should include checks for enabled SNMP services and proper credential management to prevent exploitation of similar buffer overflow vulnerabilities.