Ssh-2.0-cisco-1.25 Vulnerability Official

The SSH protocol begins with a server identification string (RFC 4253, section 4.2):

| 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 |

While the string itself is not a vulnerability, it acts as a , identifying the potential presence of a class of unpatched legacy software. The risk to an organization is directly tied to the gap between their current patch level and the latest Cisco security advisories. For legacy systems displaying this banner, the potential for a complete system compromise through remote code execution is real. For modern, unpatched ASA devices, a simple, unauthenticated packet could lock administrators out of their own firewall until a manual reboot is performed.

The SSH-2.0-Cisco-1.25 vulnerability can have significant consequences, including: ssh-2.0-cisco-1.25 vulnerability

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Currently, the "story" for this version involves two major security concerns: 1. The Terrapin Attack (CVE-2023-48795)

To help evaluate the risk posture of your device,Additionally, knowing if your device is or directly exposed to the internet will help tailor the exact patch path. Share public link The SSH protocol begins with a server identification

Many Cisco devices using the SSH stack were found to be vulnerable to the Terrapin attack .

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

The most severe threat impacting systems aligned with this software stack is a . For modern, unpatched ASA devices, a simple, unauthenticated

This banner typically indicates a Cisco device running an outdated SSH server implementation (likely from an older IOS release). The actual vulnerability most often associated with this banner is (and related issues like CVE-2009-4408), which concerns a weakness in Cisco’s SSH v2 implementation.

access-list 100 permit tcp <trusted-networks> any eq 22 line vty 0 4 access-class 100 in

show ip ssh

Robust network-level filtering is essential. Administrators should implement strict ACLs on all network infrastructure devices to restrict SSH access exclusively to dedicated management subnets, jump hosts, and bastion servers. It is crucial to verify that the ACL implementation supports filtering for the specific features in use. A recent vulnerability (CVE-2025-20159) demonstrated that some ACL implementations were bypassed for SSH and other management features, so validation is key.

: A Man-in-the-Middle (MitM) attacker intercepts the handshake negotiation between the client and the Cisco SSH server.