All but three security and network appliances from Barracuda Networks contain undocumented backdoor accounts that allow remote access over SSL and VPN.
on Thursday warned of the backdoor accounts affecting the company’s appliances: Spam and Virus Firewall, Web Filter, Message Archiver, Web Application Firewall, Link Balancer, Load Balancer and SSL VPN.
The backdoor accounts were placed there by Barracuda as part of its remote support function, however security researcher Stefan Viehböck of SEC Consult Vulnerability Lab has found they were poorly implemented.
The undocumented accounts in the appliances are for the usernames “product”, “support” and “websupport”, according to H-Security. Others included “root”, “shutdown”, “qa_test”.
The accounts were protected by passwords that Viehböck was able to quickly crack with a “tiny” wordlist, which might be fine if SSL access was limited to Barracuda’s own support staff.
Barracuda whitelisted all but two IP address ranges that it used for the task, however the researcher found the ranges also contained servers from unaffiliated third parties -- “all of whom can access SSH on all affected Barracuda Networks appliances exposed to the Internet,” he noted.
In an alert on Thursday, Barracuda gave the threat a “medium” rating but advised clients nonetheless to apply the patch “immediately”.
The patch changes the sshd configurations to only allow the users “cluster” and “remote” access under a login and public/private key arrangement; while the username “root” is secured with a login and password/password hash.
“This still leaves considerable risks to appliances as the password for the 'root' user might be crackable and the relevant private keys for the 'remote' user might be stolen from Barracuda Networks,” says Viehböck.
“In secure environments it is highly undesirable to use appliances with backdoors built into them. Even if only the manufacturer can access them.”
Barracuda played down the threat, pointing out that only an attacker with specific internal knowledge of Barracuda appliances could pull off the attack from a small set of IP addresses.
Nonetheless, Viehböck recommends putting the appliances behind a firewall and blocking any incoming local and internet traffic to port 22 -- the port that the appliances accept traffic on by default.