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.
Understanding the SSH-2.0-Cisco-1.25 Vulnerability: Risks, Identification, and Mitigation
# Disable weak Diffie-Hellman groups ip ssh dh min size 2048 # Specify secure ciphers (prefer CTR or GCM modes) ip ssh server algorithm encryption aes256-ctr aes192-ctr aes128-ctr # Specify secure Message Authentication Codes (MACs) ip ssh server algorithm mac hmac-sha2-256 hmac-sha2-512 Use code with caution. Copied to clipboard Step 3: Obfuscate the Banner (Optional)
If a network scan reveals devices reporting this version string, immediate action is required. ssh-2.0-cisco-1.25 vulnerability
The most famous vulnerability associated with this version string is the Cisco "Small SSH" issue. Early implementations of SSH on Cisco IOS had a flaw in the key exchange mechanism. In certain configurations, an attacker could bypass authentication entirely. If a device reports this version string, it is highly likely susceptible to authentication bypass, allowing an attacker to gain administrative access without a password.
While the banner itself is not a flaw, it has been a persistent marker across nearly two decades of SSH-related issues, ranging from minor interoperability quirks in older Cisco CatOS systems to serious security vulnerabilities in modern software. This article explores the context of the SSH-2.0-Cisco-1.25 banner, the significant vulnerabilities associated with Cisco’s SSH implementations, and the critical steps for securing these devices.
Many Cisco devices running the 1.25 stack are vulnerable to the , a prefix truncation weakness. The string is the standard software banner transmitted
While SSH-2.0-Cisco-1.25 itself is not the name of a singular vulnerability, it represents a massive . Security scanners (like Nessus, Greenbone, or Shodan) look for this precise banner to flag unpatched systems that are highly susceptible to critical remote execution flaws, cryptographic degradation attacks, and denial-of-service exploits.
Organizations running devices that broadcast the SSH-2.0-Cisco-1.25 identifier must immediately implement a multi-layered remediation framework to shield infrastructure from exploitation. Step 1: Restrict Management Access with Infrastructure ACLs
This banner is typically found on:
Understanding the "SSH-2.0-Cisco-1.25" Vulnerability Matrix: Risks, Technical Deep Dive, and Mitigation Strategies
If the output returns SSH-2.0-Cisco-1.25 , the device is broadcasting the targeted string. Step-by-Step Mitigation Guide