Critical SSH Backdoor in multiple Barracuda Networks

SEC Consult Vulnerability Lab Security Advisory < 20130124-0 >


title: Critical SSH Backdoor in multiple Barracuda Networks


vulnerable products: Barracuda Spam and Virus Firewall

Barracuda Web Filter

Barracuda Message Archiver

Barracuda Web Application Firewall

Barracuda Link Balancer

Barracuda Load Balancer

Barracuda SSL VPN

(all including their respective virtual "Vx" versions)

vulnerable version: all versions < Security Definition 2.0.5

fixed version: Security Definition 2.0.5

impact: Critical


found: 2012-11-20

by: S. Viehböck

SEC Consult Vulnerability Lab


Vendor/product description:




Vulnerability overview/description:


1) Backdoor accounts

Several undocumented operating system user accounts exist on the appliance.

They can be used to gain access to the appliance via the terminal but also

via SSH. (see 2)

These accounts are undocumented and can _not_ be disabled!

2) Remote access via SSH

An SSH daemon runs on the appliance, but network filtering (iptables) is used

to only allow access from whitelisted IP ranges (private and public).

The public ranges include servers run by Barracuda Networks Inc. but also

servers from other, unaffiliated entities - all of whom can access SSH on all

affected Barracuda Networks appliances exposed to the Internet.

The backdoor accounts from 1) can be used to gain shell access.

This functionality is entirely undocumented and can only be disabled via a

hidden 'expert options' dialog (see Workaround).


Proof of concept:


URLs and other exploit code (passwords) have been removed from this advisory.

A detailed advisory will be released within a month including the omitted



1) Backdoor accounts

The passwd and shadow file show that the following accounts exist.

Some passwords could be recovered (short attack with tiny wordlist):

root:x:0:0:root:/root:/bin/bash <-- UID: 0!

<hash removed>

NOT CRACKED during given time (confirmed static in tested appliances)

build:x:0:0:Build User:/root:/boot/os_tools/ <-- UID: 0!

<hash removed>

NOT CRACKED during given time

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown -h now

<hash removed>

CRACKED <password removed>


<hash removed>

CRACKED <password removed>

ca:x:704:65534:ACL reset user:/home/ca:/home/emailswitch/code/firmware/current/bin/

<hash removed>

CRACKED <password removed>


<hash removed>

CRACKED <password removed>


<hash removed>

CRACKED <password removed>


<hash removed>

NOT CRACKED during given time

The following users have public keys added to their authorized_keys


remote:x:0:0:Remote Access:/home/remote:/bin/bash <-- UID: 0!
# cat /home/remote/.ssh/authorized_keys2
ssh-dss AAAAB3NzaC1kc3MAAACBAM3angjOeIjCePKw8a/zTugPKK+hoYkpQhyXY8+BN
Q3sgpXBhW6YT+rqrJLgc9l3Y2/exVGJjYA== manager@support01.barracudanetwo

# cat /home/cluster/.ssh/authorized_keys2
ssh-dss AAAAB3NzaC1kc3MAAACBAJ5O8UhVP3lb0Mff66uHMkvcZlxPJF/7pgtcq5Qd/

At least the user "product" can be used to login and get a shell on the


It was confirmed that this user can access the MySQL database (root@localhost

with no password) eg. to add new users with administrative privileges to the

appliance configuration.

Furthermore it was possible to enable diagnostic/debugging functionality

which could be used to gain root access on the system. (confirmed in

Barracuda SSL VPN)


2) Remote access via SSH

An /etc/sysconfig/iptables file shows which rules are in place:

# Generated by iptables-save v1.2.7a on Thu Oct  9 16:39:19 2003
:PREROUTING ACCEPT [4012:488438]
:OUTPUT ACCEPT [641:40599]
# Completed on Thu Oct  9 16:39:19 2003
# Generated by iptables-save v1.2.7a on Thu Oct  9 16:39:19 2003
:INPUT ACCEPT [42408:13197223]
:OUTPUT ACCEPT [49685:7341128]
-A INPUT -s localhost -p tcp -m tcp --dport 22 -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 --tcp-flags SYN,RST,ACK SYN -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 --tcp-flags SYN,RST,ACK SYN -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 --tcp-flags SYN,RST,ACK SYN -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 -j ACCEPT 
-A INPUT -s -p tcp -m tcp --dport 22 --tcp-flags SYN,RST,ACK SYN -j ACCEPT 
-A INPUT -p tcp -m tcp --dport 22 -j REJECT --reject-with icmp-port-unreachable 
# Completed on Thu Oct  9 16:39:19 2003


The timestamp and the version of iptables-save suggest that these rules might

have been in place on Barracuda Networks appliances since 2003.

Users from these networks can access the SSH daemon running (by default on the

tested appliances) on port 22 e.g. by using the backdoor accounts:

* Private IP ranges

In some situations a user might be able to set his IP address (in the local

network) to one within the private ranges and then be allowed to access SSH.

* Public IP ranges

These ranges include some servers run by Barracuda Networks eg. ( ( ( ( (


but also servers from other entities: ( - Domain registered by: Domains By Proxy, LLC ... ( - Domain registered by: Thor Myhrstad ( - Domain registed by: Medallia Inc. ( - Domain registered by: Connectify Networks, Inc. ( - Domain registed by: WhitePages, Inc. ( - Domain registered by: Total Quality Maintenance, Inc ( - Domain registered by: HM hosting


More information about the hosts in these /24 networks can be found at:

A breach of any server in the whitelisted ranges enables an attack against all

affected Barracuda Networks appliances on the web.


The credentials from 1) (eg. "product" user) can be used to get a shell

on a appliance.


Vulnerable / tested versions:


The vulnerability has been verified to exist in Barracuda SSL VPN version, which was the most recent version at the time of discovery.

Barracuda Networks confirmed that _all_ of their appliances with the exception

of the Barracuda Backup Server, Barracuda Firewall, and Barracuda NG Firewall

are affected as well in _all_ available versions.


Vendor contact timeline:


2012-11-29: Contacting vendor.

2012-11-29: Sending advisory and proof of concept exploit via encrypted


2012-12-04: Vendor confirms receipt and provides BNSEC IDs.

2012-12-05: Requesting further coordination (conference call).

2012-12-13: Sending reminder regarding SEC Consult disclosure policy.

2012-12-15: Vendor responds - arranging conference call.

2012-12-18: Conference call: Addressing the risks the discovered

vulnerabilities pose to customers and release schedule.

2013-01-14: Vendor sends listing of reported vulnerabilities and release


2013-01-21: Conference call - discussing implemented solutions.

2013-01-21: Vendor provides information about some questions which came up.

2013-01-22: Asking for definitive listing of affected appliances.

2013-01-23: Barracuda Networks releases alert & secdef

2013-01-24: SEC Consult releases coordinated security advisory.




Update to Security Definition 2.0.5.

This will change the sshd config to only allow logins from the following users:

* cluster (login with pubic/private key)

* remote (login with pubic/private key, Barracuda Networks is in possession

of the corresponding private key)

* root (login with password, password hash (listed above) might be crackable

depending on password strength)

According to Barracuda Networks these accounts are essential for customer

support and will not be removed.

The vulnerability described in 2) is _not_ handled by this patch.

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.

In secure environments it is highly undesirable to use appliances with

backdoors built into them. Even if only the manufacturer can access them.




Place the appliances behind a firewall and block any incoming traffic

(local and Internet) to port 22.

Barracuda Networks offers an expert option that disables the SSH daemon.

For assistance contact the Barracuda Networks Support.


Advisory URL:




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EOF S. Viehböck / @2013