CVE-2023-21693: Windows 10 Printer Driver Info Disclosure

CVE-2023-21693 Overview

CVE-2023-21693 is an information disclosure vulnerability affecting the Microsoft PostScript and PCL6 Class Printer Driver. This vulnerability allows an authenticated attacker with low privileges to potentially access sensitive information from affected Windows systems through a network-based attack vector. The vulnerability requires user interaction to be exploited successfully.

Critical Impact

Successful exploitation of this vulnerability could allow attackers to disclose sensitive information from memory, potentially exposing confidential data or system information that could be leveraged for further attacks.

Affected Products

• Microsoft Windows 10 (all versions including 1607, 1809, 20H2, 21H2, 22H2)
• Microsoft Windows 11 (21H2, 22H2)
• Microsoft Windows Server 2008, 2012, 2016, 2019, 2022

Discovery Timeline

• 2023-02-14 - CVE-2023-21693 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-21693

Vulnerability Analysis

This information disclosure vulnerability exists within the Microsoft PostScript and PCL6 Class Printer Driver component of Windows operating systems. The vulnerability is classified as CWE-125 (Out-of-Bounds Read), indicating that the printer driver improperly reads data from memory locations outside the intended boundaries.

When processing certain printer-related operations, the affected driver fails to properly validate memory boundaries, allowing an attacker to read data from adjacent memory regions. This out-of-bounds read condition can expose sensitive information that resides in memory, such as heap metadata, stack canaries, or other confidential data structures.

The attack requires the attacker to be authenticated with low-level privileges on the target system and necessitates user interaction, such as convincing a user to open a malicious document or interact with a crafted printer configuration. The confidentiality impact is high, though no direct impact to system integrity or availability has been identified.

Root Cause

The root cause of CVE-2023-21693 is an out-of-bounds read vulnerability (CWE-125) in the PostScript and PCL6 printer driver. The driver fails to properly validate buffer boundaries when processing print-related data, allowing read operations beyond allocated memory regions. This improper bounds checking enables attackers to access memory contents that should not be readable, resulting in information disclosure.

Attack Vector

The attack vector for this vulnerability is network-based and requires the following conditions:

1. The attacker must have authenticated access to the target system with low privileges
2. User interaction is required - the victim must perform an action such as opening a malicious document or interacting with a specially crafted printer configuration
3. The attacker sends malicious input that triggers the out-of-bounds read condition in the printer driver
4. Sensitive information from memory is disclosed to the attacker

The vulnerability does not allow for code execution or modification of system data, but the disclosed information could potentially be used to bypass security protections like ASLR or to obtain sensitive data for subsequent attacks.

Detection Methods for CVE-2023-21693

Indicators of Compromise

• Unusual printer driver activity or crashes in the Windows Event Log
• Unexpected memory access patterns in printer spooler-related processes
• Abnormal network traffic involving print services from authenticated users
• Error events related to mscms.dll, pscript5.dll, or PCL6 driver components

Detection Strategies

• Monitor Windows Event Logs for printer driver-related errors or crashes, particularly those involving memory access violations
• Implement application whitelisting to detect unauthorized printer driver activity
• Deploy endpoint detection and response (EDR) solutions to monitor for suspicious process behavior involving the print spooler service
• Enable enhanced logging for the Print Spooler service to capture detailed driver activity

Monitoring Recommendations

• Configure Windows Event Forwarding to centralize print spooler logs for security analysis
• Establish baseline behavior for printer driver operations and alert on deviations
• Monitor for unusual authentication patterns followed by printer-related activities
• Use SentinelOne's behavioral AI engine to detect anomalous memory access patterns indicative of out-of-bounds read attempts

How to Mitigate CVE-2023-21693

Immediate Actions Required

• Apply the security update from Microsoft's February 2023 Patch Tuesday release immediately
• Prioritize patching systems that handle sensitive data or are accessible from untrusted networks
• Review and restrict printer driver installations to trusted sources only
• Consider disabling the Print Spooler service on systems where printing functionality is not required

Patch Information

Microsoft has released security updates to address CVE-2023-21693 as part of the February 2023 security updates. The official security advisory and patches are available through the Microsoft Security Response Center. Organizations should deploy the appropriate update for their Windows version through Windows Update, WSUS, or manual deployment.

Workarounds

• Disable the Print Spooler service on systems where printing is not required using the command below
• Implement network segmentation to limit exposure of print services
• Restrict printer driver installation to administrators only through Group Policy
• Apply the principle of least privilege to limit the potential impact of exploitation

# Disable Print Spooler service as a temporary workaround
Stop-Service -Name Spooler -Force
Set-Service -Name Spooler -StartupType Disabled

# Verify the service is disabled
Get-Service -Name Spooler | Select-Object Name, Status, StartType