Cisco has addressed an almost maximum severity authentication bypass Enterprise NFV Infrastructure Software vulnerability with public proof-of-concept exploit code.

CVE-2021-34746 is caused by incomplete validation of user-supplied input passed to an authentication script during the sign-in process which allows unauthenticated, remote attackers to log into unpatched device as an administrator.

“An attacker could exploit this vulnerability by injecting parameters into an authentication request,” Cisco explained in a security advisory published on Wednesday.

“A successful exploit could allow the attacker to bypass authentication and log in as an administrator to the affected device.”

To check if a device is vulnerable to CVE-2021-34746 exploits, you must check if the TACACS external authentication feature is toggled on.

Cisco said no workarounds are available to remove the attack vector exposed by this security flaw, but fixed the issue in Cisco Enterprise NFVIS releases 4.6.1 and later.