Ssh-2.0-cisco-1.25 Vulnerability !exclusive!

October 26, 2023 Target Service: SSH-2.0-Cisco-1.25 Severity: High to Critical (Context Dependent)

Older versions may leak system data or memory contents during the initial handshake phase.

: Cisco-1.25 alone does not confirm any specific CVE. It must be cross-referenced with show version output. ssh-2.0-cisco-1.25 vulnerability

A severe flaw historically mapped to Cisco’s SSHv2 engine involves authentication bypasses. In specific versions of Cisco IOS and IOS XE software configured for Rivest, Shamir, and Adleman (RSA)-based public-key user authentication, a logical failure in the validation engine allowed unauthenticated remote users to bypass authentication mechanisms entirely.

However, this banner serves as an accurate "marker" for several categories of older, potentially vulnerable Cisco devices. The security risk is not the string itself, but the age, configuration, and patch level of the device that displays it. A device running an SSH server that identifies as version 1.25 is highly likely to be running a legacy software release that, in turn, is vulnerable to any of the numerous Cisco SSH-related CVEs that have been published over the last two decades. October 26, 2023 Target Service: SSH-2

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

At its core, SSH-2.0-Cisco-1.25 is the protocol version string sent by Cisco's SSH server implementation. This specific identifier is typically associated with Cisco Internetwork Operating System (IOS) and Catalyst Operating System (CatOS) devices that have SSH support enabled. A severe flaw historically mapped to Cisco’s SSHv2

Recent reports have identified a critical vulnerability (CVSS 10.0) in certain Cisco products using the Erlang/OTP SSH implementation. It allows unauthenticated remote code execution by sending connection protocol messages before authentication occurs.

: A MitM attacker can silently delete or truncate specific packets, downgrading the encryption protocols to weaker ciphers or disabling vital authentication security extensions without the client or server realizing a breach occurred. Technical Remediation and Hardening Strategy

On supported devices, the SSH configuration should be hardened to disable all weak and deprecated cryptographic primitives. This includes explicitly disabling key exchange algorithms like diffie-hellman-group1-sha1 , which are commonly required for compatibility with older devices. Administrators should also disable older protocol versions and weaker cipher suites where possible.

Flaws found in modern IOS and IOS XE distributions allow unauthorized users to repeatedly knock critical network infrastructure offline.