CVE-2018-25263

Executive Summary

CVE-2018-25263 is a local buffer overflow vulnerability in Faleemi Desktop Software version 1.8.2. The flaw resides in the Device alias field within the Managing Log interface. A local attacker can craft a malicious payload that overwrites the Structured Exception Handler (SEH), leading to arbitrary code execution. The vulnerability has a CVSS score of 8.4, indicating high severity, but the EPSS score is 0.0%, suggesting low exploitation likelihood in the wild. No official patch is available, and the vendor status is unknown.

CVSS Breakdown & Threat Level

• CVSS Score: 8.4 (High)
• Attack Vector: Local (AV:L)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

The high CVSS score reflects the ability to execute arbitrary code with low privileges and no user interaction, though the attack is limited to local access.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in the Device alias field. The application does not properly validate the length of the input before copying it into a fixed-size buffer. By providing an overly long string, the attacker can overwrite the SEH chain on the stack. When an exception occurs, the overwritten SEH handler is invoked, redirecting execution to attacker-controlled shellcode.

The exploit typically involves:

1. Crafting a payload that fills the buffer, overwrites the SEH pointer, and includes shellcode.
2. Pasting the payload into the Device alias field in the Managing Log interface.
3. Triggering an exception (e.g., by causing a crash) to execute the SEH handler.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the original Faleemi Desktop Software 1.8.2. The patched version would need to implement input validation and bounds checking on the Device alias field. A secure implementation would limit the input length and use safe string copy functions (e.g., strncpy instead of strcpy).

Exploitation & Lab Setup

Red Team

Lab Setup:

• Windows 7/10 VM with Faleemi Desktop Software 1.8.2 installed.
• Debugger (e.g., Immunity Debugger) to analyze the crash.
• Python or Metasploit to generate payload.

Exploit Steps:

1. Identify the offset to SEH overwrite using a pattern (e.g., pattern_create.rb).
2. Generate a payload with shellcode (e.g., msfvenom -p windows/exec CMD=calc.exe -f python).
3. Craft the exploit string: [padding] + [SEH overwrite] + [nop sled] + [shellcode].
4. Paste the string into the Device alias field.
5. Trigger the exception to execute the SEH handler.

Example Python PoC:

import struct

# Offset to SEH (example, adjust based on actual crash)
offset = 1000
seh = struct.pack('<I', 0x90909090)  # Placeholder for SEH address

# Shellcode to execute calc.exe
shellcode = b"\x31\xc9\x51\x68\x63\x61\x6c\x63\x54\xb8\xc7\x93\xbf\xb0\xff\xd0"

payload = b"A" * offset + seh + b"\x90" * 100 + shellcode

print(payload)

Blue Team

Detection:

• Monitor for unusually long input in the Device alias field.
• Use application whitelisting to prevent unknown executables.
• Enable Structured Exception Handler Overwrite Protection (SEHOP) if available.

Mitigation:

• Apply input validation at the application level.
• Use DEP and ASLR to make exploitation harder.
• Consider replacing the software with a patched alternative.

Indicators of Compromise (IOCs)

• File: Faleemi Desktop Software executable (e.g., Faleemi.exe) with version 1.8.2.
• Registry: Unusual entries in HKEY_CURRENT_USER\Software\Faleemi.
• Network: No network IOCs as the attack is local.
• Process: Unexpected child processes (e.g., calc.exe) spawned by Faleemi.exe.
• Memory: SEH chain pointing to user-controlled data.

Detection Engineering

YARA Rule

rule CVE_2018_25263_Faleemi_SEH_Overwrite {
    meta:
        description = "Detects Faleemi Desktop Software 1.8.2 with potential SEH overwrite"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2018-25263"
    strings:
        $s1 = "Faleemi Desktop Software" wide ascii
        $s2 = "1.8.2" wide ascii
        $s3 = "Device alias" wide ascii
    condition:
        all of them
}

Sigma Rule

title: Faleemi SEH Overwrite Exploit Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2018-25263 via long input in Device alias field
author: Valters IT
logsource:
    category: application
    product: faleemi
detection:
    selection:
        EventID: 1000  # Application crash
        Application: "Faleemi.exe"
        ExceptionCode: 0xc0000005  # Access violation
    condition: selection
falsepositives:
    - Legitimate crashes due to other reasons
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2018-25263 Faleemi SEH Overwrite Attempt"; content:"Device alias"; depth:100; pcre:"/Device alias.{0,1000}/"; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Disable or uninstall Faleemi Desktop Software 1.8.2 until a patch is available.
• Workaround: Restrict local access to the application and monitor for unusual input.
• Long-term: Contact the vendor for a patched version or migrate to an alternative solution.
• Compensating Controls: Enable SEHOP, DEP, and ASLR on the host system.

Valters IT

{/* [Security Hash: 49CE9B980E85EBA1ED11DC09] */}