CVE-2024-20399

CVE-2024-20399 is a command injection flaw (CWE-78) in the CLI of Cisco NX-OS Software, caused by insufficient validation of arguments passed to specific configuration CLI commands. An authenticated attacker who already holds Administrator credentials can trigger it by submitting crafted input as the argument of an affected configuration command, gaining the ability to execute arbitrary commands as root on the device's underlying operating system. Because Administrator access is required, the flaw is effectively a privilege-escalation issue following credential compromise, and it grants no additional privilege on Nexus 3000 Series, Nexus 7000 Series running NX-OS 8.1(1) or later, and Nexus 9000 Series in standalone NX-OS mode, which already allow administrative bash-shell access to the OS. Any organization running affected NX-OS on Cisco Nexus switching is in scope, with the practical risk concentrated in environments where admin credentials may have been stolen. Exploitation has been observed in the wild: the China-linked group 'Velvet Ant' (associated with Salt Typhoon) used it as a zero-day to compromise U.S. ISPs and telecom providers, and CISA added it to the Known Exploited Vulnerabilities catalog on 2024-07-02.

What to do: Upgrade affected Nexus switches to a fixed NX-OS release per Cisco's security advisory, as required by the CISA KEV listing (apply mitigations per vendor instructions or discontinue use if fixes are unavailable). Restrict and audit Administrator-level CLI access on NX-OS devices, and hunt for suspicious configuration-command activity or unexplained root-level actions, given Velvet Ant/Salt Typhoon targeting of telecom and ISP networks. For Nexus 3000, Nexus 7000 (8.1(1)+), and Nexus 9000 standalone-mode devices the flaw adds no privilege, but patching is still recommended.