CVE-2025-11641

Executive Summary

CVE-2025-11641 identifies a critical improper access control vulnerability in Tomofun Furbo 360 and Furbo Mini pet cameras. The flaw resides in the Trial Restriction Handler component, allowing an attacker with physical access to the device to bypass trial restrictions and potentially gain unauthorized control. The attack complexity is high, and exploitability is difficult, but the impact could lead to full device compromise, including unauthorized video/audio streaming and manipulation of device settings. No patch has been released by the vendor, and no public exploit code is available.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector assigned)
• Attack Vector: Physical (requires physical access to the device)
• Attack Complexity: High (requires specific timing or hardware manipulation)
• Privileges Required: None (physical access is sufficient)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High (potential access to live video/audio)
• Integrity Impact: High (ability to modify device settings)
• Availability Impact: High (potential to disable device)
• Threat Level: High (due to physical access requirement, but severe impact if exploited)

Deep Dive & Mechanics

The vulnerability exists in the Trial Restriction Handler, a component that enforces trial period limitations on the Furbo devices. By manipulating this handler, an attacker can bypass trial restrictions, potentially enabling full functionality without a valid subscription. The exact mechanism is not publicly disclosed, but it likely involves:

• Firmware-level bypass: Exploiting a flaw in the firmware's logic for checking trial status.
• Hardware manipulation: Using physical access to reset or modify the trial counter.
• Side-channel attacks: Timing or power analysis to bypass the restriction check.

The affected firmware versions are Furbo 360 up to FB0035_FW_036 and Furbo Mini up to MC0020_FW_074. The vendor has not responded to disclosure, leaving devices unpatched.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable code is in the Trial Restriction Handler, which likely contains a logic flaw such as:

// Vulnerable pseudocode
if (trial_expired == TRUE) {
    restrict_functionality();
} else {
    allow_full_access();
}
// Attacker can manipulate trial_expired flag via physical access

A patched version would require:

// Patched pseudocode
if (trial_expired == TRUE) {
    if (verify_hardware_signature() == VALID) {
        restrict_functionality();
    } else {
        // Tamper detected, lock device
        lock_device();
    }
} else {
    allow_full_access();
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Physical access to a Furbo 360 or Furbo Mini device.
• Basic hardware tools (e.g., JTAG debugger, UART adapter, multimeter).
• Knowledge of the device's firmware and boot process.

Exploitation Steps:

1. Identify the Trial Restriction Handler: Use firmware analysis (e.g., binwalk, Ghidra) to locate the handler code.
2. Bypass the Restriction: Modify the trial status flag in memory or flash storage via:
   • UART/JTAG: Connect to the debug interface and overwrite the flag.
   • Firmware modification: Extract, patch, and reflash the firmware.
3. Verify Access: After bypass, the device should allow full functionality without a subscription.

No public exploit code is available.

Blue Team

Detection:

• Monitor for physical tampering (e.g., opened casing, debug port activity).
• Log firmware version and trial status changes.
• Use network monitoring to detect unusual device behavior (e.g., unexpected streaming).

Mitigation:

• Isolate devices on a separate VLAN.
• Enable tamper detection (if available).
• Regularly check for firmware updates.

Indicators of Compromise (IOCs)

• Firmware Hash: SHA256 of modified firmware (unknown, but can be computed if exploit is developed).
• Network Traffic: Unusual outbound connections from the device to unknown IPs.
• Device Logs: Entries indicating trial status changes or debug port access.
• Physical Signs: Opened casing, exposed debug headers, or soldering marks.

Detection Engineering

YARA Rule

rule CVE_2025_11641_TrialBypass {
    meta:
        description = "Detects modified Furbo firmware with trial restriction bypass"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-11641"
    strings:
        $trial_flag = "trial_expired" nocase
        $bypass_code = { 90 90 90 90 } // NOP sled example
    condition:
        $trial_flag and $bypass_code
}

Sigma Rule

title: Furbo Trial Restriction Bypass Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects physical tampering or firmware modification on Furbo devices
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "trial_status: modified"
        - "debug_port: opened"
        - "firmware_hash: *"
    condition: selection
falsepositives:
    - Legitimate firmware updates
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-11641 Furbo Trial Bypass - Unusual Outbound Traffic"; flow:to_server; content:"|00 01 02 03|"; depth:4; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Disconnect affected devices from the internet until a patch is available.
• Physical Security: Restrict physical access to devices.
• Firmware Update: Monitor Tomofun's website for a firmware update (none available as of now).
• Workaround: If possible, disable trial features or use a firewall to block device communication.
• Long-term: Replace devices with patched versions or alternative products.

Valters IT
Securing Digital Frontiers