Ssh-2.0-cisco-1.25 Vulnerability |link| May 2026

The identifier "SSH-2.0-Cisco-1.25" is not a standard CVE (Common Vulnerabilities and Exposures) number, but rather a specific SSH banner string observed on some older Cisco devices.

This banner typically indicates a Cisco device running an outdated SSH server implementation (likely from an older IOS release).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 CVE-2011-1322 (and related issues like CVE-2009-4408), which concerns a weakness in Cisco’s SSH v2 implementation.

Below is a practical guide to understanding, detecting, and mitigating the risk.

Phase 4: Continuous Monitoring

Deploy SNMP traps for SSH login failures.
Use NetFlow to detect anomalous SSH connection attempts.
Re-scan quarterly with credentialed vulnerability scans (not just banner grabs).

5. False positives & notes

Some newer Cisco devices (e.g., IOS-XE, NX-OS) may also show Cisco-1.25 but are not vulnerable – the banner string was reused in some later builds. Always check the actual IOS version.
Tools like Nessus or OpenVAS might flag SSH-2.0-Cisco-1.25 as “potential vulnerability” – verify manually.

Final Note

If you are required to submit this as a formal paper for academic or professional use, I strongly recommend that you:

Verify actual affected versions via Cisco’s official PSIRT database.
Replace the sample CVE mappings with real matches after checking the device’s true software version.
Add a real lab demonstration (e.g., Metasploit module, custom SSH fuzzing).

Would you like me to help you instead:

Find real CVEs affecting specific Cisco versions (if you can provide the exact IOS version),
Write a detection script for such banners, or
Generate a vulnerability report template based on a real CVE (e.g., CVE-2015-6294)?

Understanding the "SSH-2.0-Cisco-1.25" Banner and Modern Security Risks

If you have recently run a vulnerability scan like Nessus or OpenVAS against your Cisco infrastructure, you may have seen a reference to SSH-2.0-Cisco-1.25. 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?

This is a software banner identifying the SSH server running on your Cisco device. SSH-2.0: Indicates the device is running SSH Version 2. ssh-2.0-cisco-1.25 vulnerability

Cisco-1.25: Refers to a specific legacy version of the Cisco SSH stack found in various Cisco IOS, IOS XE, and older PIX/ASA software releases.

Because this version is dated, it is frequently flagged by scanners because it supports weak cryptographic algorithms or is susceptible to protocol-level attacks discovered in recent years. Top Vulnerabilities Linked to This Version

When security professionals discuss the "Cisco-1.25 vulnerability," they are typically referring to one of the following critical issues: 1. The Terrapin Attack (CVE-2023-48795)

Many Cisco devices running the 1.25 stack are vulnerable to the Terrapin attack, a prefix truncation weakness.

The Risk: A Man-in-the-Middle (MitM) attacker can downgrade the connection's security by deleting specific protocol messages during the handshake without the client or server noticing. Cisco Bug ID: CSCwi61646. 2. Unauthenticated Remote Code Execution (CVE-2025-32433)

Recent advisories have highlighted a maximum-severity flaw (CVSS 10.0) in certain Cisco SSH implementations (specifically those utilizing Erlang/OTP libraries).

The Risk: Attackers can execute arbitrary code on the target system without needing to authenticate first. The identifier "SSH-2

Affected Banner: This has been observed in environments reporting the SSH-2.0-Cisco-1.25 banner. 3. Weak Cryptographic Algorithms

Older Cisco SSH stacks often default to algorithms now considered "broken" or "weak":

KEX Algorithms: Support for diffie-hellman-group1-sha1 or diffie-hellman-group-exchange-sha1.

Ciphers: Continued use of CBC-mode ciphers (e.g., aes128-cbc), which are susceptible to side-channel attacks. How to Secure Your Cisco Device

If your scanner has flagged this banner, follow these steps to mitigate the risk: Step 1: Update Your IOS/IOS XE Software

The most effective fix is to upgrade to a modern, patched version of Cisco software. Check the Cisco Security Advisory for your specific hardware to find the recommended "Gold Star" release. Step 2: Harden the SSH Configuration

If you cannot upgrade immediately, manually disable weak algorithms in the CLI: Phase 4: Continuous Monitoring

# Disable weak Diffie-Hellman groups ip ssh dh min size 2048 # Specify secure ciphers (prefer CTR or GCM modes) ip ssh server algorithm encryption aes256-ctr aes192-ctr aes128-ctr # Specify secure Message Authentication Codes (MACs) ip ssh server algorithm mac hmac-sha2-256 hmac-sha2-512 Use code with caution. Copied to clipboard Step 3: Obfuscate the Banner (Optional)

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 Terrapin (CVE-2023-48795) 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.

Are you seeing this alert on a specific model, like a Catalyst switch or an ASA firewall? Providing the hardware type can help narrow down the exact patch you need.

B. Permanent fix – Upgrade IOS

Upgrade to a fixed IOS version:

12.4(24)T5 or later
12.2(33)SXI5 or later
15.0(1)M1 or later
Any 15.1+ release

Check Cisco’s advisory for your exact hardware and feature set.

D. End-of-Life (EOL) / End-of-Support (EOS) Risks

Devices reporting SSH-2.0-Cisco-1.25 are often running software that has reached End-of-Life. This means they no longer receive security patches for newly discovered vulnerabilities, making them a persistent security liability.