Fix: Ssh-2.0-cisco-1.25 Vulnerability

The most critical vulnerabilities associated with Cisco SSH implementations (which often report this banner) include: Critical Vulnerabilities Authentication Bypass (CVE-2015-6280) : A flaw in the SSHv2 public key authentication

Navigate directly to the official Cisco Software Checker tool. Enter the exact OS or IOS XE version number extracted from your device to see if it belongs to an affected branch. Step 3: Implement Immediate Infrastructure Mitigations

This is a software banner identifying the SSH server running on your Cisco device. : Indicates the device is running SSH Version 2. ssh-2.0-cisco-1.25 vulnerability

The is a prefix truncation weakness in the SSH protocol. It allows a Man-in-the-Middle (MitM) attacker to delete messages during the initial handshake without the client or server noticing. SSH Terrapin Prefix Truncation Weakness - Cisco Community

Perhaps the most significant technical quirk relates to cryptographic agility. Many devices that display the SSH-2.0-Cisco-1.25 banner often require older, insecure key exchange algorithms like diffie-hellman-group1-sha1 . This algorithm uses a 1024-bit prime modulus, which is considered insufficient against modern computational capabilities and well-funded adversaries. The default disabling of these weak algorithms in modern, secure SSH clients directly causes connectivity failures to these older Cisco devices. The most critical vulnerabilities associated with Cisco SSH

These attacks were not theoretical. Government agencies discovered active exploitation in the wild, where attackers were using these flaws to execute arbitrary code, bypass authentication, and potentially exfiltrate sensitive data from compromised devices. The fact that these zero-days were discovered in actively exploited campaigns underscores the high value that sophisticated attackers place on compromising Cisco infrastructure.

0 Helpful. Georg Pauwen. VIP Alumni. ‎02-16-2021 12:30 AM. Hello, I think the '1.25' part is the Cisco specific vendor version ID. Cisco Community : Indicates the device is running SSH Version 2

When auditing infrastructure displaying this banner, security teams typically evaluate the system against several critical Cisco security advisories.

: A Man-in-the-Middle (MitM) attacker can downgrade the connection's security by deleting specific protocol messages during the handshake without the client or server noticing. Cisco Bug ID : CSCwi61646 . 2. Unauthenticated Remote Code Execution (CVE-2025-32433)

Router(config)# ip ssh time-out 60 Router(config)# ip ssh authentication-retries 3 Use code with caution.

Addressing the risks associated with devices displaying the SSH-2.0-Cisco-1.25 banner requires a multi-layered approach, combining immediate tactical fixes with long-term strategic upgrades.