CVE-2017-6743 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: CSCve60376, CSCve78027.
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Analysis
by VulDB Data Team • 07/31/2025
The vulnerability identified as CVE-2017-6743 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 networking infrastructure. The vulnerability specifically targets the SNMP processing mechanisms that handle incoming network packets, creating a potential entry point for remote code execution or system reload conditions. The buffer overflow occurs during the parsing of SNMP packets, where insufficient input validation allows maliciously crafted data to overwrite adjacent memory regions, potentially leading to arbitrary code execution or denial of service scenarios.
The technical exploitation of this vulnerability requires an authenticated remote attacker who can send specially crafted SNMP packets to the targeted system via either IPv4 or IPv6 protocols. The attack vector is particularly concerning because it leverages the standard network management protocols that are commonly enabled on network devices for monitoring and administration purposes. For SNMP versions 2c and earlier, attackers must possess the valid SNMP read-only community string to successfully exploit the vulnerability, while SNMP Version 3 requires valid user credentials including proper authentication and authorization parameters. This distinction in attack requirements demonstrates the varying levels of privilege needed based on the SNMP version being targeted, though all versions remain susceptible to the underlying buffer overflow condition. The vulnerability affects all SNMP versions 1, 2c, and 3, indicating that the flaw exists at a fundamental level within the SNMP processing architecture rather than being version-specific.
The operational impact of CVE-2017-6743 extends beyond simple network disruption to potentially enable complete system compromise through remote code execution. When exploited successfully, the buffer overflow could allow attackers to execute arbitrary code with the privileges of the SNMP process, potentially leading to full system compromise. The vulnerability's ability to cause system reloads creates additional operational concerns as it could be used to perform denial of service attacks against critical network infrastructure. Devices that have SNMP enabled and have not explicitly excluded vulnerable MIBs or OIDs are considered at risk, meaning that default Cisco configurations without proper security hardening would be susceptible to exploitation. This widespread exposure is particularly dangerous in enterprise environments where SNMP is commonly enabled for network monitoring purposes, creating a significant attack surface that could be exploited by malicious actors to gain unauthorized access to network infrastructure.
Organizations should implement immediate mitigations including disabling SNMP if not required for network management operations, implementing proper SNMP community string management with strong, unique credentials, and applying the relevant Cisco security patches released to address this vulnerability. Network segmentation and access control measures should be enhanced to limit the scope of potential exploitation, particularly by implementing firewalls that restrict SNMP traffic to authorized management systems only. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of how network protocol implementations can create security risks when proper input validation and memory management practices are not implemented. From an ATT&CK framework perspective, this vulnerability maps to techniques involving remote code execution and privilege escalation, potentially enabling attackers to establish persistent access to network infrastructure. Regular vulnerability assessments and network monitoring should be conducted to identify systems that may be running vulnerable versions of Cisco IOS or IOS XE, with particular attention to devices that have SNMP enabled but lack proper security configurations to prevent unauthorized access.