Ssh-2.0-cisco-1.25 Vulnerability Hot! (VERIFIED — 2027)

: The authentication step is entirely bypassed. The attacker gains immediate terminal access matching the elevated privileges of the target VTY lines. 4. Denial of Service (DoS) Through Resource Exhaustion

: This is the internal version of the Cisco SSH software implementation. Cisco Community Why Scanners Flag This

Upgrade the device firmware to a supported release and regenerate RSA keys.

may also be susceptible to other well-documented SSH weaknesses if not fully patched: SSH Terrapin Prefix Truncation Weakness - Cisco Community

In networking, is a basic footprinting technique used by administrators and attackers alike to discover the operating system and version running on a remote port. When a client connects to a Cisco router or switch via SSH, the exchange begins with a text string formatted like this: SSH-[Protocol Version]-[Software Version] ssh-2.0-cisco-1.25 vulnerability

When a vulnerability scanner flags SSH-2.0-Cisco-1.25 , it means the scanner has detected a Cisco device running a generic or legacy version of Cisco’s internal SSH engine. Because this banner string remains identical across multiple firmware iterations, it can maps to several potential vulnerabilities depending on the specific underlying Cisco IOS release.

Vulnerabilities related to SSH host key validation have also been identified. CVE-2025-20163 in the Cisco Nexus Dashboard Fabric Controller (NDFC) allows an unauthenticated, remote attacker to impersonate NDFC-managed devices. The flaw is due to insufficient SSH host key validation, which enables a machine-in-the-middle (MitM) attack. An attacker in a position to intercept network traffic could capture and decrypt SSH sessions meant for the legitimate device.

Classified with a CVSS v3.1 score of 10.0 , indicating maximum severity.

A more recent vulnerability (CVSS 5.3, Medium) was found in the SSH server of Cisco Adaptive Security Appliance (ASA) Software. The flaw is a logic error that occurs when an SSH session is established. An unauthenticated, remote attacker could exhaust available SSH resources by sending crafted SSH messages. This leads to a state where all new SSH connections are denied, causing a DoS condition for remote management, and the device must be to restore SSH service. : The authentication step is entirely bypassed

SSH0: Exchanging versions - SSH-2.0-Cisco-1.25 SSH0: send SSH message: outdated is NULL server version string:SSH-2.0-Cisco-1.25

: Inefficient memory management handles protocol exceptions poorly.

If SSH is not required and the device cannot be upgraded, disable the SSH service entirely and manage the device via console cable (out-of-band management) to remove the remote attack vector.

The SSH-2.0-Cisco-1.25 banner is a relic of a previous era of network management. Seeing this banner on a network device today should be considered a significant operational risk indicator. It almost always points to an older system with potential interoperability issues, weak cryptographic defaults, and a susceptibility to a wide range of unpatched vulnerabilities, including those that enable denial of service, remote command execution, and bypass of security controls. Denial of Service (DoS) Through Resource Exhaustion :

In certain scenarios involving specific versions of Cisco products, unauthenticated RCE vulnerabilities have been linked to Erlang/OTP SSH components used within Cisco infrastructure, making older SSH implementations high-risk. Potential Risks and Impact

More severe is the discovery of remote command injection vulnerabilities. CVE-2024-20329, affecting Cisco ASA Software with the CiscoSSH stack enabled, allows an authenticated, remote attacker to execute operating system commands as root . This is due to insufficient validation of user input within the SSH subsystem. An attacker with valid but low-privileged credentials can leverage this flaw to gain complete control over the security appliance.

The most critical step is to keep your Cisco software up to date.

This is a software banner identifying the SSH server running on your Cisco device. : Indicates the device is running SSH Version 2.

The string SSH-2.0-Cisco-1.25 is not a specific vulnerability itself, but rather the software version banner

Given the long history and varied nature of SSH issues on Cisco devices, a layered and proactive security strategy is essential. Here are the key steps to secure your network infrastructure.