CVE-2026-20177 in Industrial Ethernet Switches
Summary
by MITRE • 08/19/2026
A vulnerability in the handling of management plane packets by Cisco Industrial Ethernet (IE) 1000 Series Switches could allow an unauthenticated, remote attacker to cause the device manager, SSH, or API to become inaccessible.This vulnerability is due to insufficient protection against management plane flooding attacks. An attacker could exploit this vulnerability by sending a high rate of ICMP, SSH, or HTTP traffic to an affected device. A successful exploit could allow the attacker to cause the CPU of the device to increase, resulting in a denial of service (DoS) condition on the device manager web GUI, SSH, or API. Data traffic through the device is not affected.
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Analysis
by VulDB Data Team • 08/19/2026
The Cisco Industrial Ethernet 1000 Series Switches contain a critical vulnerability within their management plane packet handling mechanisms that exposes network infrastructure to denial of service attacks originating from unauthenticated remote sources. This flaw stems directly from insufficient protection against management plane flooding, which allows an attacker to overwhelm the device's control resources by generating high volumes of specific protocol traffic. The affected protocols include Internet Control Message Protocol (ICMP), Secure Shell (SSH), and Hypertext Transfer Protocol (HTTP). Because the vulnerability targets the management interface rather than the data forwarding plane, it represents a significant risk for operational technology environments where remote access to switches is essential for configuration and monitoring but often lacks robust rate-limiting or authentication prerequisites on all entry points.
From a technical perspective, the exploitation of this vulnerability relies on saturating the CPU resources dedicated to processing management traffic rather than packet switching operations. When an attacker sends a high rate of ICMP echo requests, SSH connection attempts, or HTTP API calls without proper authentication or throttling limits, the switch's processor becomes consumed by these administrative tasks. This resource exhaustion leads directly to a denial of service condition for legitimate administrators attempting to access the device manager web GUI, establish secure shell sessions, or interact with the application programming interface. It is crucial to note that this impact is isolated to management functions; data traffic passing through the switch remains unaffected and continues to forward normally, meaning production networks may continue operating while administrative control is lost.
The operational impact of this vulnerability extends beyond simple unavailability of configuration tools. In industrial settings where network stability and rapid troubleshooting are paramount, losing access to SSH or the web GUI can prevent timely response to other security incidents or performance issues. Furthermore, because the attack requires no authentication, it lowers the barrier for entry significantly, allowing any actor with network connectivity to disrupt administrative capabilities. This aligns closely with CWE-787: Out-of-bounds Write in terms of resource exhaustion logic and is categorized under ATT&CK technique T1498: Network Denial of Service, specifically focusing on layer 3/layer 4 impacts that degrade service availability for authorized users while leaving underlying data paths intact.
Mitigation strategies must focus on hardening the management plane against flooding attacks since patching may not be immediately available in all legacy industrial environments. Administrators should implement strict rate limiting on ICMP, SSH, and HTTP traffic destined for the switch's IP addresses using access control lists or hardware-based policing features if supported by the IOS version. Additionally, restricting management access to known trusted source IPs via ACLs reduces the attack surface significantly. Enabling authentication mechanisms such as AAA with TACACS+ or RADIUS ensures that only verified users can initiate sessions, thereby neutralizing the unauthenticated aspect of this exploit. Regularly updating firmware to versions where Cisco has addressed these specific rate-limiting gaps is also essential for long-term resilience against management plane attacks.