Pierluigi Paganini April 02, 2021

Unpatched vulnerabilities in QNAP small office/home office (SOHO) network-attached storage (NAS) devices could be exploited by remote attackers to remotely execute arbitrary code.

Security researchers at SAM Seamless Network discovered a couple of critical unpatched flawsin QNAP small office/home office (SOHO) network-attached storage (NAS) devices that could allow remote attackers to execute arbitrary code on vulnerable devices.

The vulnerabilities affect QNAP TS-231 SOHO NAS devices running firmware version 4.3.6.1446 that reached end of life (EOL).

“These vulnerabilities are severe in nature as they allow for full takeover of device from the network including access to the user’s stored data, without any prior knowledge.” reads the advisory published by SAM Seamless Network.

The first vulnerability is an RCE issue that affects any QNAP device exposed to the Internet, it resides in the NAS web server (default TCP port 8080).

Experts focused their analysis on some cgi files, most of them are available through the web server at /mnt/HDA_ROOT/home/httpd/cgi-bin directory on the TS-231 file system.

“During the inspection, we fuzzed the web server with customized HTTP requests to different cgi pages, with focus on those that do not require prior authentication. We’ve been able to generate an interesting scenario, which triggers remote code execution indirectly (i.e., triggers some behavior in other processes).” continues the advisory.

Experts suggest to fix the issue by implementing input sanitizations to some core processes and library APIs, unfortunately the issue has yet to be fixed.

Below the timeline for this issue:

• October 12, 2020 – Full disclosure reported to QNAP security team.
• October 23, 2020 – Sent another e-mail to QNAP security team.
• October 31, 2020 – Automatic reply from “QNAP support” with a ticket number.
• January 26, 2021 – Sent a notification to QNAP about end of the grace period (which is planned to end on February 12).
• January 26, 2021 – Reply from QNAP Helpdesk: the problem is confirmed but still in progress.
• February 12, 2021 – Grace period has elapsed.
• March 31, 2021 – Initial blog post published.

The second vulnerability is an arbitrary file write vulnerability that resides in the DLNA server (default TCP port 8200) which handles UPNP requests on this port. The vulnerability could be exploited by remote attackers to execute arbitrary code on a remote NAS device.

Below the timeline for this vulnerability:

• November 29, 2020 – Full disclosure reported to QNAP security team. No reply from QNAP has been received yet for this specific disclosure.
• March 29, 2021 – Grace period has elapsed.
• March 31, 2021 – Initial blog post has been published.

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Pierluigi Paganini

(SecurityAffairs – hacking, SOHO)

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