Ssh-2.0-cisco-1.25 Vulnerability Work Jun 2026

Organizations should implement continuous monitoring for suspicious SSH traffic. This includes detection of brute-force attempts, unusual numbers of authentication failures, unexpected cryptographic negotiations, and anomalous connection patterns from unauthorized source IP addresses. SIEM integration and network traffic analysis tools can help identify early signs of compromise.

: The device runs into an unhandled exception state and triggers a forced system reload, generating a sustained Denial of Service (DoS) window across the production environment. 3. RSA-Based Public Key Authentication Bypass ssh-2.0-cisco-1.25 vulnerability

: Recent reports in April 2025 highlight a critical RCE vulnerability in the Erlang-based SSH server used in some Cisco product lines. This is a "Perfect 10" severity flaw that allows unauthenticated code execution. Cisco Community How to Verify and Mitigate SSH Terrapin Prefix Truncation Weakness - Cisco Community : The device runs into an unhandled exception

| CVE | Description | Fixed in | |------|-------------|-----------| | | SSHv2 server DoS via crafted SSH packet → reload | IOS 15.1(2)T, 15.2(1)T | | CVE-2015-6274 | Algorithm negotiation bypass → weak encryption forced | IOS 15.4(3)M, 15.5(3)M | | CVE-2016-6376 | Memory exhaustion via multiple SSHv2 key exchanges | IOS 15.5(3)M3 | | CVE-2018-0151 | Remote code execution via SSHv2 (rare, but present in older banners) | IOS 15.6(3)M2 | This is a "Perfect 10" severity flaw that

: An unauthenticated, remote attacker can send specially crafted connection protocol messages over the network to bypass security restrictions entirely. This allows for arbitrary code execution directly within the system shell, leading to a complete compromise of the underlying infrastructure, data manipulation, and lateral movement. The Terrapin Attack (CVE-2023-48795)

If you see this banner, the device is likely vulnerable to one or more of the following:

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.