CVE-2025-11635

Executive Summary

CVE-2025-11635 identifies a resource consumption vulnerability in the Tomofun Furbo 360 pet camera, specifically in firmware version FB0035_FW_036. The flaw resides in the file upload component, allowing an unauthenticated remote attacker to cause excessive resource consumption, leading to a denial of service (DoS) condition. The vendor has not responded to disclosure attempts, and no patch is currently available. This vulnerability poses a risk to IoT devices in home environments, potentially disrupting monitoring capabilities.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD base score not assigned; calculated as 7.5 based on vector)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)
• Threat Level: High – Remote, unauthenticated DoS with no user interaction.

Deep Dive & Mechanics

The vulnerability is triggered by sending a specially crafted file upload request to the Furbo 360 device. The file upload component fails to properly validate or limit the size, frequency, or content of uploads, leading to exhaustion of system resources such as memory, CPU, or storage. This can cause the device to become unresponsive, crash, or reboot, effectively denying service to legitimate users. The attack is remotely exploitable over the network, likely via the device's HTTP or proprietary API endpoints.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code resides in the firmware's file upload handler. A hypothetical fix would involve:

• Implementing file size limits.
• Rate limiting upload requests.
• Validating file types and content.
• Adding resource monitoring and throttling.

Vulnerable Code (Conceptual):

void handle_file_upload(char *data, int size) {
    // No size check
    char *buffer = malloc(size);
    memcpy(buffer, data, size);
    // Process file...
}

Patched Code (Conceptual):

#define MAX_FILE_SIZE 1048576 // 1 MB

void handle_file_upload(char *data, int size) {
    if (size > MAX_FILE_SIZE) {
        return_error("File too large");
        return;
    }
    char *buffer = malloc(size);
    if (buffer == NULL) {
        return_error("Out of memory");
        return;
    }
    memcpy(buffer, data, size);
    // Process file...
}

Exploitation & Lab Setup

Red Team

1. Reconnaissance: Scan for Furbo 360 devices on the local network using Shodan or Nmap.

   nmap -p 80,443,554,5000 --open 192.168.1.0/24
   

2. Exploit: Send a large file upload request to the device's file upload endpoint.

   curl -X POST -F "file=@/dev/urandom;size=1000000000" http://<target-ip>/upload
   

3. Denial of Service: Repeat the request multiple times to exhaust resources.

Blue Team

1. Monitor Network Traffic: Detect abnormal file upload sizes or frequencies.
2. Rate Limiting: Implement network-level rate limiting for upload endpoints.
3. Firmware Update: Check for vendor updates; if unavailable, isolate the device on a separate VLAN.
4. Log Analysis: Review device logs for repeated upload attempts.

Indicators of Compromise (IOCs)

• Network: High volume of HTTP POST requests to /upload endpoint with large payloads.
• System: Device becomes unresponsive, high CPU/memory usage, frequent reboots.
• Logs: Entries indicating file upload failures or resource exhaustion errors.

Detection Engineering

YARA Rule

rule CVE_2025_11635_Furbo_DoS {
    meta:
        description = "Detects large file upload attempts targeting Furbo 360"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $http_post = "POST /upload" ascii nocase
        $large_size = "Content-Length: [0-9]{7,}" ascii
    condition:
        $http_post and $large_size
}

Sigma Rule

title: Furbo 360 File Upload DoS Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects large file uploads to Furbo 360 devices
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/upload'
        sc-bytes|gte: 10000000
    condition: selection
falsepositives:
    - Legitimate large file uploads (unlikely for IoT camera)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-11635 Furbo 360 File Upload DoS"; flow:to_server; content:"POST"; http_method; content:"/upload"; http_uri; content:"Content-Length|3a|"; http_header; pcre:"/Content-Length:\s*\d{7,}/"; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Disable remote access to the Furbo 360 device. Use firewall rules to block inbound traffic to the device's upload endpoint.
• Short-term: Monitor vendor channels for a firmware patch. If none is released, consider replacing the device.
• Long-term: Implement network segmentation for IoT devices. Use a web application firewall (WAF) to filter large uploads.
• Workaround: If the device supports it, disable the file upload feature via the mobile app or device settings.

Valters IT
Securing Digital Frontiers