Vulnerability: Ssh-2.0-cisco-1.25

: Block all internet-facing traffic targeting TCP Port 22. Restrict SSH inbound permissions exclusively to specific, isolated Management VLANs or secure Jump Host IP blocks.

A critical vulnerability (CVSS 9.9) was also discovered in the SSH subsystem of Cisco ASA and Firepower Threat Defense (FTD) Software. This issue, due to insufficient input validation, allowed an authenticated, remote attacker to execute commands on the underlying operating system with by sending crafted input during SSH sessions.

Internal flaws inside the Cisco-1.25 software state machine expose core enterprise routing switches to memory corruption and unexpected crashes.

! Disable SSHv1 entirely no ip ssh version 1 ip ssh version 2

Cisco has released software updates to address these vulnerabilities across its product lines. Administrators are advised to: ssh-2.0-cisco-1.25 vulnerability

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

The vulnerability affects devices configured for RSA-based user authentication (public key).

More severe is the discovery of remote command injection vulnerabilities. CVE-2024-20329, affecting Cisco ASA Software with the CiscoSSH stack enabled, allows an authenticated, remote attacker to execute operating system commands as root . This is due to insufficient validation of user input within the SSH subsystem. An attacker with valid but low-privileged credentials can leverage this flaw to gain complete control over the security appliance.

Attackers can downgrade the connection's overall security, disable extension negotiations (like public-key keystroke obfuscation), and exploit subtle flaws in standard block ciphers. : Block all internet-facing traffic targeting TCP Port 22

This is a prefix truncation attack that targets the SSH protocol's integrity. CSCwi61646 - SSH Terrapin Prefix Truncation ... - Cisco Bug

Disclaimer: The information in this article is based on publicly available Cisco Security Advisories and security research reports from 2023-2025.

that a Cisco device displays when you connect to its SSH server.

A critical vulnerability linked to network components using Erlang-based subsystems allows unauthenticated remote code execution (RCE). This issue, due to insufficient input validation, allowed

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The core issue is a vulnerability in the SSHv2 implementation of Cisco IOS software. A crafted SSHv2 packet can cause the device to crash or reload.

ip ssh server algorithm encryption aes256-gcm aes128-gcm ip ssh server algorithm mac hmac-sha2-512 hmac-sha2-256 Use code with caution.

Where possible, replace password-based SSH authentication with strong, ed25519 or RSA (3072-bit or higher) key pairs. This eliminates the risk of password brute-forcing and mitigates several classes of authentication vulnerabilities. Key-based authentication should be enforced alongside proper revocation mechanisms to prevent unauthorized access if a key is compromised.