Ssh20cisco125 Vulnerability: Exclusive

: Implement robust authentication mechanisms. Utilize multi-factor authentication wherever possible.

Immediately apply the latest patches issued by Cisco. It is highly recommended to use the Cisco Software Checker to verify your software status.

Potential Remote Code Execution (RCE) or device reload. ssh20cisco125 vulnerability exclusive

On firewalls running Cisco Adaptive Security Appliance (ASA) Software , vulnerabilities exist depending on which SSH engine is utilized. In certain versions (like ASA 9.18 and 9.20), the system is vulnerable if the administrator has disabled the newer Cisco SSH architecture. Running the CLI check:

Legacy SSH version 1 is fundamentally broken and insecure. Restrict all device lines to SSHv2 exclusively to mitigate protocol-level downgrade attacks: Device(config)# ip ssh version 2 Use code with caution. : Implement robust authentication mechanisms

If an attacker gains access to a backup server containing ASA configuration files, they can extract usernames and their public keys. With this information, they can remotely log in to the ASA devices without ever obtaining the corresponding private keys.

| CVE / Advisory | Description | Severity | |---|---|---| | | SSH private‑key authentication bypass in ASA proprietary stack | Medium (5.3) | | CVE‑2026‑20080 | DoS against SSH service on IEC6400 Wireless Backhaul Edge Compute Software | Medium (5.3) | | CVE‑2026‑1626 | Weak CBC‑based cipher suites in SSH service | Medium | | Cisco Bug CSCvx63027 | DoS via SSH leading to device reload on IOS and IOS XE | Not yet scored | | Cisco Bug CSCwh52374 | SSH client privilege escalation on IOS XR for 8000/NCS routers | Not yet scored | | Cisco Bug CSCwp27755 | Static SSH credentials in Cisco Unified Communications Manager (development credentials) | Not yet scored | | CVE‑2025‑20159 | ACL bypass for SSH on IOS XR | Medium (5.3) | | CVE‑2025‑20163 | SSH host key validation failure on NDFC (MitM attack) | Not yet scored | | CVE‑2025‑32433 | RCE in Erlang/OTP SSH server (critical, affects multiple Cisco products) | Critical (10.0) | It is highly recommended to use the Cisco

Since Cisco has not yet released a patch, defenders must apply and compensating controls :

In tests, the leak occurs in the ssh_kex_hash debug buffer, which prints up to 125 bytes of adjacent memory—hence the "125" in the name.

Server management interfaces (IMC) are prime targets for attackers because they provide out-of-band management access. Organizations should apply the principle of least privilege to IMC accounts and consider segmenting management traffic onto dedicated, heavily monitored VLANs.

Leaked debug logs suggest the flaw resides in the crypto_ssh_kex_cisco_int function—a proprietary Cisco enhancement to the SSH key exchange that handles legacy KEX algorithms (e.g., diffie-hellman-group-exchange-sha1 ).