CVE-2025-66676

Executive Summary

CVE-2025-66676 identifies a Denial of Service (DoS) vulnerability in IObit Unlocker version 1.3.0.11. The flaw allows an attacker to cause the application to crash or become unresponsive by sending a crafted request. This vulnerability is classified under CWE-20 (Improper Input Validation), indicating that the software does not properly validate input before processing it, leading to an unexpected state. The EPSS score is 0.0%, suggesting a low probability of exploitation in the wild at this time. No public proof-of-concept (PoC) code or exploit is currently available. The vendor, Iobit, has not released a patch, and the status remains UNKNOWN.

Supply Chain & Package Security

This vulnerability does not affect NPM, PyPI, Go, or Ruby packages. It is a standalone Windows application vulnerability.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is unusual and likely indicates that a full CVSS vector has not been assigned or published by NVD. Based on the description, a reasonable assessment would be:

• Attack Vector (AV): Network (N) – The crafted request can be sent over a network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication is needed.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The vulnerability only affects the vulnerable component.
• Confidentiality (C): None (N) – No data is exposed.
• Integrity (I): None (N) – No data is modified.
• Availability (A): High (H) – The service becomes unavailable.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Estimated Base Score: 7.5 (High)

Threat Level: High (Availability impact only). The lack of a patch and the ease of exploitation (network-based, no auth) make this a significant risk for availability.

Deep Dive & Mechanics

The vulnerability resides in IObit Unlocker, a utility designed to unlock files that are in use by other processes. The application likely listens for inter-process communication (IPC) or handles specific command-line arguments or network requests. The "crafted request" likely triggers a buffer overflow, null pointer dereference, or an infinite loop due to improper input validation.

Potential Attack Vector:

1. Local Exploitation: An attacker with local access could send a malformed IPC message to the running IObit Unlocker service.
2. Remote Exploitation (Less Likely but Possible): If the application exposes a network service (e.g., a named pipe accessible over the network or a TCP/UDP listener), a remote attacker could send the crafted request.

Root Cause: The application fails to sanitize or validate the size, format, or content of the input request. This could lead to:

• Buffer Overflow: Writing data beyond the allocated buffer, corrupting memory and causing a crash.
• Null Pointer Dereference: The input causes the application to access a memory address that is null.
• Infinite Loop: The input triggers a loop that never terminates, consuming CPU resources.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison cannot be made. However, the vulnerable code likely resembles:

Vulnerable Code (Conceptual C++):

void ProcessRequest(char* input) {
    char buffer[256];
    strcpy(buffer, input); // No bounds checking
    // ... process buffer
}

Patched Code (Conceptual):

void ProcessRequest(char* input, size_t input_len) {
    char buffer[256];
    if (input_len >= sizeof(buffer)) {
        // Log error and reject
        return;
    }
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // ... process buffer
}

The patched version would include input length validation and use safe string copy functions.

Exploitation & Lab Setup

Red Team (Exploitation)

Since no public exploit is available, a penetration tester would need to reverse-engineer the application to identify the vulnerable input vector. The following steps outline a potential approach:

1. Setup: Install IObit Unlocker v1.3.0.11 on a Windows 10/11 VM.
2. Reconnaissance: Use tools like Process Monitor (Procmon), API Monitor, or a debugger (x64dbg) to monitor how the application handles input.
3. Fuzzing: Use a fuzzer (e.g., Peach Fuzzer, Boofuzz) to send malformed data to any identified IPC endpoints (named pipes, sockets, or window messages).
4. Crash Analysis: When a crash occurs, analyze the crash dump to determine the exact input that caused it.
5. Exploit Development: Craft a specific request that reliably triggers the DoS.

Example Fuzzing Script (Python with boofuzz):

from boofuzz import *

def main():
    session = Session(
        target=Target(connection=SocketConnection("127.0.0.1", 12345, proto="tcp")),
    )
    define_protocol(session)
    session.connect(session.root)
    session.fuzz()

def define_protocol(session):
    s_initialize("Request")
    s_string("UNLOCK", fuzzable=True)
    s_delim(" ")
    s_string("C:\\path\\to\\file", fuzzable=True)
    s_static("\r\n")

if __name__ == "__main__":
    main()

Blue Team (Detection & Defense)

1. Monitor for Crashes: Enable Windows Error Reporting (WER) and monitor for repeated crashes of IObitUnlocker.exe.
2. Network Monitoring: If the application listens on a network port, monitor for unusual traffic patterns or malformed packets targeting that port.
3. Process Monitoring: Use Sysmon or EDR to detect when IObitUnlocker.exe is launched with unusual command-line arguments or receives unexpected IPC messages.
4. Honeypot: Deploy a decoy instance of IObit Unlocker to capture potential exploit attempts.

Indicators of Compromise (IOCs)

• File Hash (SHA256): [Unknown - Obtain from a clean installation of v1.3.0.11]
• Process Name: IObitUnlocker.exe
• Network Signature: Unusual traffic to/from the host on ports commonly used by IObit Unlocker (if any).
• Event Logs:
  • Windows Application Event Log: Event ID 1000 (Application Error) for IObitUnlocker.exe.
  • Sysmon Event ID 1 (Process Creation) with IObitUnlocker.exe and suspicious command-line arguments.
• Registry: Modifications to HKLM\SOFTWARE\IObit\Unlocker (if any).

Detection Engineering

YARA Rule

rule CVE_2025_66676_IObit_Unlocker_DoS {
    meta:
        description = "Detects IObit Unlocker v1.3.0.11 binary"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "unknown"
    strings:
        $s1 = "IObit Unlocker" wide ascii
        $s2 = "1.3.0.11" wide ascii
        $s3 = "Unlocker.exe" wide ascii
    condition:
        all of them and filesize < 5MB
}

Sigma Rule

title: CVE-2025-66676 - IObit Unlocker DoS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2025-66676 via process crashes
author: Valters IT
date: 2025/04/10
logsource:
    category: application
    product: windows
detection:
    selection:
        EventID: 1000
        ApplicationName: 'IObitUnlocker.exe'
    condition: selection
falsepositives:
    - Legitimate crashes due to other software conflicts
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-66676 IObit Unlocker DoS Attempt"; flow:to_server; content:"UNLOCK"; depth:6; content:"|0d 0a|"; within:10; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Since no patch is available, consider uninstalling IObit Unlocker v1.3.0.11 and using an alternative tool (e.g., Microsoft's handle.exe or LockHunter).
2. Network Segmentation: If the application must be used, ensure it is not exposed to untrusted networks.
3. Least Privilege: Run the application with the minimum necessary privileges.
4. Monitoring: Implement the detection rules provided above to identify potential exploitation attempts.
5. Vendor Contact: Contact IObit support to request a patch or workaround.
6. Virtualization: Run the application in a sandboxed environment (e.g., Windows Sandbox) to limit the impact of a DoS.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert