If you have recently run a vulnerability scan like Nessus or OpenVAS against your Cisco infrastructure, you may have seen a reference to . While this string is actually a version banner rather than a single specific "vulnerability," it often serves as a primary indicator for several critical security flaws affecting Cisco’s SSH implementation. What is SSH-2.0-Cisco-1.25?

By delivering a corrupted or specific malformed sequence during public-key authentication, an attacker can trick the protocol parser into granting an administrative command-line interface (CLI) session without requiring valid secret keys. 2. Reverse SSH Username DoS (CVE-2012-0388)

The SSH-2.0-Cisco-1.25 vulnerability is caused by a buffer overflow in the SSH protocol implementation. An attacker can exploit this vulnerability by sending a specially crafted SSH packet to the device, which can lead to:

: A flaw in validation mechanics lets a remote actor bypass standard cryptographic check boundaries.

| CVE ID | Description | Affected Versions (Example) | |--------|-------------|-----------------------------| | CVE-2007-1242 | SSH v1 buffer overflow (legacy) | Cisco IOS 12.2-12.4 | | CVE-2010-0567 | SSH v2 memory corruption | Cisco IOS 12.2(25) series | | CVE-2015-6294 | SSH key exchange algorithm downgrade | Cisco IOS-XE 3.13S |

: By carefully removing or truncating data sequence numbers during the packet exchange, the attacker fools the system into lowering its security posture.

This timeline helps visualize the long lifespan of the issues associated with this banner.

If you see SSH-2.0-Cisco-1.25 , the device be vulnerable, but you must verify the IOS version.

An attacker can send specific protocol messages before authenticating, exploiting a memory or logic error in how the SSH server handles early communication.