Ssh-2.0-cisco-1.25 Vulnerability [FHD 2024]

While "security by obscurity" isn't a primary defense, you can prevent casual scanning from identifying your exact version. On some platforms, you can customize or suppress parts of the SSH banner via the banner command, though the protocol-level version string (Cisco-1.25) is often hard-coded into the stack. Summary Table Vulnerability Mitigation Security Downgrade Disable ChaCha20-Poly1305 and CBC ciphers. RCE (CVE-2025-32433) Full System Takeover Immediate software update/patching. Weak KEX/Ciphers Data Decryption Update ip ssh settings to use SHA-2 and CTR.

A vulnerability scan or nmap script scan of a device with this banner typically returns results similar to the following:

SSH-<protocol version>-<software version> <comments>

1. The Core Vulnerabilities Associated with SSH-2.0-Cisco-1.25 ssh-2.0-cisco-1.25 vulnerability

Cisco IOS Software Reverse SSH Denial of Service Vulnerability

The “Cisco-1.25” likely refers to an internal version tag used in Cisco’s SSH implementation. This may correspond to:

Crafting an SSH inbound request using an invalid or specifically malformed reverse-login username causes an unhandled memory exception inside the Cisco internal SSH state machine. The operating system crashes and forces a cold reboot. 3. Weak Cryptographic Cipher Suites While "security by obscurity" isn't a primary defense,

The presence of ssh-2.0-cisco-1.25 is rarely a false positive for trouble. It correlates with several major security weaknesses:

An unpatched instance broadcasting the SSH-2.0-Cisco-1.25 profile may be vulnerable to several critical flaws in Cisco's SSH state machines and protocol engines: 1. Authentication Bypass (CVE-2015-6280)

devices. While the banner itself is not a vulnerability, it helps attackers identify the underlying software to target specific known flaws. Cisco Community The Core Vulnerabilities Associated with SSH-2

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.

Security scanners (like Nessus or Qualys) often flag this banner because it reveals the device's operating system and version, which can help an attacker identify known vulnerabilities. Below is a breakdown of what this banner means and the actual vulnerabilities often associated with it. What is SSH-2.0-Cisco-1.25?

: Multiple product lines, including those running specific versions of IOS XE and other platforms that integrate the affected Erlang/OTP SSH server components. Würth Phoenix Additional Associated Risks Devices reporting Cisco-1.25

Another vulnerability (often tracked alongside Cisco SSH issues) allows an authenticated attacker to cause an affected device to reload unexpectedly.