CVE-2017-6736 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: CSCve57697.
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Analysis
by VulDB Data Team • 07/31/2025
The vulnerability identified as CVE-2017-6736 represents a critical buffer overflow condition within the Simple Network Management Protocol subsystem of Cisco IOS and IOS XE software versions. This flaw affects a broad range of Cisco networking equipment including routers and switches running versions 12.0 through 12.4 and 15.0 through 15.6 of IOS, along with IOS XE versions 2.2 through 3.17. The security implications are severe as the vulnerability can be exploited remotely by authenticated attackers to achieve arbitrary code execution or system reloads, fundamentally compromising network infrastructure integrity. The vulnerability manifests specifically within the SNMP processing mechanisms where insufficient input validation leads to memory corruption when handling crafted SNMP packets.
The technical exploitation of this vulnerability requires an attacker to send specifically crafted SNMP packets to the targeted device over either IPv4 or IPv6 networks. This attack vector aligns with the ATT&CK framework's technique T1071.004 for application layer protocol usage and T1203 for exploitation for execution. The buffer overflow occurs during SNMP packet processing where the system fails to properly validate the length of incoming data, allowing an attacker to overflow allocated memory buffers. This condition is classified as a CWE-121 buffer overflow vulnerability that enables attackers to overwrite adjacent memory locations and potentially execute malicious code. The attack requires authentication for exploitation, with different credential requirements based on SNMP version used - community strings for versions 1 and 2c, and user credentials for SNMPv3.
The operational impact of CVE-2017-6736 extends beyond simple system compromise as it can lead to complete network infrastructure disruption through unauthorized code execution or denial of service via system reloads. Organizations with SNMP-enabled devices running vulnerable software are at significant risk since these devices typically serve as network management endpoints that attackers can target to gain deeper network access. The vulnerability affects all SNMP versions equally, making it particularly dangerous as network administrators may believe that switching to SNMPv3 provides sufficient protection when the underlying buffer overflow remains present. This vulnerability directly impacts the CIA triad by compromising confidentiality through potential data exfiltration, integrity through unauthorized code execution, and availability through system reload attacks.
Mitigation strategies for CVE-2017-6736 should include immediate patching of affected devices with Cisco's security advisories, specifically addressing the vulnerabilities detailed in Cisco Bug ID CSCve57697. Network segmentation and access control measures should be implemented to limit SNMP access to trusted management stations only, while disabling SNMPv1 and SNMPv2c where possible in favor of the more secure SNMPv3 protocol. The principle of least privilege should be applied to SNMP user accounts, requiring strong authentication credentials and limiting the scope of accessible MIBs or OIDs. Network monitoring should be enhanced to detect anomalous SNMP traffic patterns that could indicate exploitation attempts, and devices should be configured to explicitly exclude vulnerable MIBs or OIDs that are not required for network management operations. Organizations should also consider implementing network access control lists to restrict SNMP traffic to only necessary management stations, reducing the attack surface for this particular vulnerability.