A flaw in Cisco Secure Firewall ASA's proprietary SSH stack permits an attacker who knows a valid username and the associated public key to craft input during the authentication phase and gain login privileges. The attacker does not need the private key and does not achieve root-level rights, but can execute commands as the compromised user. This represents a partial authentication bypass that may expose internal commands and data accessible to that user account.

The vulnerability impacts Cisco Secure Firewall Adaptive Security Appliance (ASA) Software. No specific product versions are listed, so all released versions of Cisco ASA that incorporate the affected SSH stack may be susceptible.

The CVSS score of 5.3 indicates moderate severity, while the EPSS score of less than 1% suggests a very low probability of exploitation in the wild. The vulnerability is not present in the CISA KEV catalog. An attacker must be able to connect to the device’s SSH service from the network, possess a valid username and the corresponding public key, and send the crafted authentication data. The attack vector is remote, unauthenticated, and requires no administrative privileges beyond normal user credentials.