CVE-2025-29803 - How Hackers Elevate Privileges via Uncontrolled Search Path in Visual Studio Tools for Applications & SQL Server Management Studio

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In early 2025, Microsoft patched a critical vulnerability tracked as CVE-2025-29803. This flaw impacts Visual Studio Tools for Applications (VSTA) and SQL Server Management Studio (SSMS). If you’re a developer or sysadmin, it's crucial to understand how this bug works, why it’s dangerous, and, most importantly, how you might secure your environment.

What is CVE-2025-29803?

CVE-2025-29803 is an Uncontrolled Search Path Element vulnerability. In plain English, this means the software runs or loads files from a folder it shouldn’t trust. Attackers can plant malicious files where the program will find and use them—without ever needing administrative rights upfront.

Why is It Dangerous?

Using carefully placed files, a user already on your machine (but with limited rights) could trick VSTA or SSMS into running their code with higher permissions. This lets them do things like:

Install malware

Even though the attacker needs local access (they must have an account on your PC/server already!), the potential damage is high.

How Does the Exploit Work?

To “exploit” this bug, an attacker leverages the way these Microsoft tools trust files in certain directories, sometimes before checking system paths.

Attacker identifies a DLL module or script that VSTA or SSMS tries to load when starting.

2. They create a malicious version of that file (often a DLL) and place it in a directory that appears in the search path before the legitimate system one.
3. The next time VSTA or SSMS is launched, it loads and executes the attacker’s code with elevated privileges.

Example Code: A Malicious DLL

Below is a *simple* example of a Windows DLL written in C (for demonstration only). When loaded, this DLL just pops up a message box—proof the attacker’s code runs:

// evil.dll - Proof of Concept DLL for CVE-2025-29803
#include <windows.h>

BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) {
    switch (ul_reason_for_call) {
        case DLL_PROCESS_ATTACH:
            MessageBoxA(, "Evil DLL loaded!", "CVE-2025-29803 POC", );
            break;
    }
    return TRUE;
}

How is this DLL used?

- Put evil.dll in a folder where VSTA or SSMS searches for it first (such as the current working directory or user-writable path).

Find the load order

Use a tool like Process Monitor to watch VSTA/SSMS and see which DLLs they search for on startup, and where.

Trigger the load

- Start the application with a working directory set to your writable path, or let it launch for you with default settings if the path is vulnerable.

Who’s at Risk?

If you run Microsoft Visual Studio Tools for Applications or SQL Server Management Studio on multi-user systems (including Remote Desktop, shared workstations, or servers), you are especially at risk. Attackers need only a low-privilege account.

- Patch immediately: Microsoft released fixes for this issue. Get them here

- VSTA Security Update
- SSMS Security Update
- Limit user write access to application directories. Don’t let ordinary users write to locations in the program’s search path.
- Use Application Whitelisting: Tools like Windows Defender Application Control can block unauthorized DLLs.

Official Microsoft Advisory:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29803

CWE-427: Uncontrolled Search Path Element

https://cwe.mitre.org/data/definitions/427.html

DLL Hijacking Overview

https://attack.mitre.org/techniques/T1574/001/

Final Thoughts

CVE-2025-29803 highlights a classic, often-overlooked Windows bug: trusting directories and files that shouldn’t be trusted. Local privilege escalation flaws like this remain a common way for hackers to move sideways—or upward—inside a breached network.

Patch, restrict, and monitor your applications. Even small missteps in search path handling can become huge opportunities for attackers.

Timeline

Published on: 04/12/2025 02:15:20 UTC
Last modified on: 04/16/2025 00:42:12 UTC