Ssh-2.0-cisco-1.25 | Vulnerability

Understanding the SSH-2.0-Cisco-1.25 Vulnerability: Risks, Identification, and Mitigation

The only true fix is to upgrade the device's firmware to a modern version of Cisco IOS or IOS-XE that supports current SSH standards (SSH v2 with AES-256 and RSA 2048-bit keys or higher).

Cisco has acknowledged multiple vulnerabilities in the SSH server of Cisco IOS and other products that could allow an unauthenticated, remote attacker to cause a denial-of-service (DoS) condition. These flaws often reside in the parsing of specific SSH packets. A malicious actor could send a crafted or malformed request that the SSH server cannot handle properly, forcing it to crash, hang, or enter an infinite loop. ssh-2.0-cisco-1.25 vulnerability

Modern vulnerability listings often flag the Cisco SSH engine for memory corruption or state machine mismanagement.

: Terrapin targets the handshake phase of the SSH protocol. It manipulates sequence numbers during the extension negotiation phase. Understanding the SSH-2

SSH-2.0-Cisco-2.22 (IOS 15.9) SSH-2.0-Cisco-2.36 (IOS-XE 16.x)

: If an attacker knew a valid local username configured for RSA authentication, a flaw in how the SSH engine parsed the key allowed entry without validating ownership of the matching private key. A malicious actor could send a crafted or

The SSH-2.0-Cisco-1.25 vulnerability is caused by a weakness in the way the SSH protocol handles authentication requests. An attacker can exploit this vulnerability by sending a specially crafted SSH packet to the device, which can cause the device to crash or allow the attacker to gain unauthorized access.

The string SSH-2.0-Cisco-1.25 is parsed into two distinct parts:

This is perhaps the oldest and most specific issue directly tied to the 1.25 version string. It is a classic interoperability flaw.

IOS 12.2(33) – 12.4(24)T IOS 15.0(1)M – 15.1(3)T