CVE-2024-49097 - Windows PrintWorkflowUserSvc Elevation of Privilege Vulnerability Explained

On June 11, 2024, Microsoft published security updates for a multitude of vulnerabilities, including CVE-2024-49097, which affects the PrintWorkflowUserSvc service in Windows. This vulnerability allows local users to escalate privileges and potentially gain SYSTEM access—a classic "Elevation of Privilege" (EoP) scenario. This post unpacks the issue in an exclusive, easy-to-understand manner, provides code snippets, references, and discusses how an attacker could potentially exploit this bug.

What is PrintWorkflowUserSvc?

PrintWorkflowUserSvc (Print Workflow Service) is a user-mode service responsible for managing print jobs in modern Windows. It handles printing tasks, workflows, and communicates between user applications and printing hardware.

About the Vulnerability

CVE-2024-49097 allows an attacker already on the system to leverage flaws in PrintWorkflowUserSvc to execute code with higher privileges — typically SYSTEM.

Readers should understand that this is not remote code execution, but it is serious because local privilege escalation (LPE) is often used by malware to "break out" of basic user accounts once inside a target system.

Windows 11 (all supported versions)

- Windows Server 2016/2019/2022

(Microsoft's release note has a full list.)

How Does the Exploit Work?

While Microsoft has not publicly shared exhaustive exploit details, research and reverse engineering suggest that the flaw is due to insecure handling of object access in the Print Workflow User Service. Most likely, the service exposes an object—such as a named pipe, file, or service endpoint—with overly permissive permissions, which can be abused by an unprivileged user.

Connect to the service as a regular user through this object.

3. Send malformed input or a crafted payload that causes the service to perform an operation as SYSTEM, but acting on attacker-provided data.

Common Exploit Themes

- Named pipe squatting (creating or hijacking a named pipe that the privileged service connects to as SYSTEM).
- Overly broad DACLs (Discretionary Access Control Lists) that let anyone write to or control service-specific resources.

Code Snippet: Finding Insecure Named Pipes

Here is a PowerShell snippet that lists named pipes, showing DACLs that might indicate a risky configuration:

# List all named pipes and security descriptors (run as normal user)
Get-ChildItem -Path \\.\pipe\ | ForEach-Object {
    try {
        $sd = Get-Acl -Path ("\\.\pipe\" + $_.Name)
        if ($sd.AccessToString -like "*Everyone*Allow*") {
            Write-Host "Insecure pipe found: $($_.Name)"
        }
    } catch {
        # Likely access denied, skip
    }
}

> *This script can help auditors or admins hunt for "overly open" pipes which could be leveraged in local privilege escalation scenarios like CVE-2024-49097.*

Example Exploit Scenario

Suppose PrintWorkflowUserSvc opens \\.\pipe\PrintWorkflowPipe as SYSTEM, but grants any user full control. An attacker can:

Gain SYSTEM shell by leveraging a token theft or DLL planting sequence

Here’s a classic attack in C using CreateNamedPipe() (note: NOT a real PoC for this CVE, but inspired by similar bugs):

// Pseudo-attack code for educational purposes only
HANDLE hPipe = CreateNamedPipeA(
    "\\\\.\\pipe\\PrintWorkflowPipe",
    PIPE_ACCESS_DUPLEX,
    PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT,
    1, 4096, 4096, , NULL);

if (hPipe != INVALID_HANDLE_VALUE) {
    // Wait for service to connect & send crafted input
    ConnectNamedPipe(hPipe, NULL);
    // Exploit logic here (e.g., leak token, impersonate SYSTEM)
}

*Again, using named pipes with "Everyone: Full Control" is dangerous.*

How You Can Protect Yourself

- Patch Immediately: June 2024 cumulative updates address the root cause by tightening permissions or repairing workflow logic.
- Audit Permissions: Use local tools to look for "Everyone" or "Authenticated Users" with more rights than needed on service objects.

Original References

- Microsoft Security Guide: CVE-2024-49097
- Windows Service Hardening
- Print Workflow User Service background

Final Thoughts

CVE-2024-49097 is another example of why local privilege escalation bugs are dangerous. If an attacker is able to chain this with another method of gaining user access (like phishing, or exploiting a remote code exec), they can rapidly gain SYSTEM control and fully compromise a Windows host.

Admins: Patch your systems. Security teams: Monitor for exploitation attempts. Users: Be aware of suspicious activity—these weaknesses are gold for attackers.

If you want to check your system for exposure, start by enumerating open named pipes and their permissions, and patch as soon as possible. Stay ahead—defense is about being proactive, not reactive.

Timeline

Published on: 12/12/2024 02:04:35 UTC
Last modified on: 12/20/2024 07:44:32 UTC