Ssh-2.0-cisco-1.25 Vulnerability

: If an environment has RSA public-key authentication configured , an attacker who discovers a valid local username can gain shell access with the underlying privileges assigned to that terminal line. 2. Device Reload and Denial of Service (CVE-2020-3200)

: The attack forces a downgrade of the connection's security profile , turning off extensions like ChaCha20-Poly1305 or Encrypt-then-MAC, leaving the active session exposed to data decryption or session hijacking. Cryptographic Degradation (Diffie-Hellman Group 1 & MD5)

The string SSH-2.0-Cisco-1.25 is a common identification banner found when connecting to Cisco IOS and IOS XE devices via Secure Shell (SSH). While the string itself is not a vulnerability, it often acts as a digital fingerprint for older, unpatched, or misconfigured network infrastructure that may be susceptible to several critical security flaws.

If the output shows:

: The device exhausts its internal buffer space, trigger an unrecoverable kernel panic, and forces the core router or switch to reload. Technical Remediation and Mitigation Steps ssh-2.0-cisco-1.25 vulnerability

: The internal Cisco software version handling the SSH process.

The string is the standard software banner transmitted by the Cisco IOS and CatOS Secure Shell (SSH) server subsystem during the initial protocol handshake. When an administrator or scanner tests an open port 22, this identity string signals that the target is a legacy or mainstream enterprise Cisco networking device.

Older firmware distributions broadcasting this exact banner have historically introduced security defects within the user validation process.

When security tools flag this banner as a "vulnerability," they are highlighting that the system is broadcasting a specific version of Cisco's proprietary internal SSH daemon. This daemon is commonly found on older enterprise routers, switches, and security appliances. Over time, various critical flaws have emerged across multiple generations of Cisco software utilizing this engine, exposing networks to authentication bypasses, denial-of-service (DoS) conditions, and potential remote exploitation. 1. Deconstructing the Banner String : If an environment has RSA public-key authentication

Under precise conditions, the system bypasses user verification, logging the unauthorized actor directly into Virtual Teletype (VTY) administrative line interfaces. Summary Table: Vulnerability Matrix for Cisco-1.25 Devices

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.

Understanding the security risks associated with this banner requires an examination of the flaws it exposes, how attackers scan for it, and the necessary remediation techniques. What Does the SSH-2.0-Cisco-1.25 Banner Mean?

The string SSH-2.0-Cisco-1.25 is a software version banner identifying the Secure Shell (SSH) server implementation used by a wide variety of Cisco products, including Catalyst switches ISR routers ASA firewalls Cryptographic Degradation (Diffie-Hellman Group 1 & MD5) The

This signature breaks down into three key functional components:

For older Cisco environments, indicates that the device mandates the secure SSH version 2.0 protocol while operating on an older internal Cisco SSH code branch ( Cisco-1.25 ). Security scanning engines parse this plaintext banner during passive reconnaissance to match the asset against historically documented vulnerabilities. Associated Historical Vulnerabilities

Below is a practical guide to understanding, detecting, and mitigating the risk.