CVE-2023-27350: PaperCut MF Auth Bypass Vulnerability

CVE-2023-27350 Overview

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SetupCompleted class. The issue results from improper access control. An attacker can leverage this vulnerability to bypass authentication and execute arbitrary code in the context of SYSTEM.

Critical Impact

Remote code execution without authentication

Affected Products

• Papercut Papercut Mf
• Papercut Papercut Ng

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to papercut
• Not Available - CVE CVE-2023-27350 assigned
• Not Available - Papercut releases security patch
• 2023-04-20 - CVE CVE-2023-27350 published to NVD
• 2025-10-27 - Last updated in NVD database

Technical Details for CVE-2023-27350

Vulnerability Analysis

CVE-2023-27350 is a critical authentication bypass vulnerability leading to remote code execution in PaperCut NG 22.0.5. This flaw is due to incorrect access controls within the SetupCompleted class, allowing attackers to gain unauthorized access and execute arbitrary commands as SYSTEM without prior authentication. The vulnerability is exploited over a network without the need for any preconditions or specific user interactions.

Root Cause

The root cause of this vulnerability is an improper implementation of access control mechanisms within the SetupCompleted class of PaperCut NG.

Attack Vector

This vulnerability is exploited via a network-based attack, allowing attackers to remotely trigger the flaw without needing local access to the affected systems.

# Example exploitation code (sanitized)
import requests

url = "http://target_address:port/SetupCompleted"
response = requests.get(url)

if response.status_code == 200:
    print("Vulnerable to authentication bypass")
else:
    print("Not vulnerable")

Detection Methods for CVE-2023-27350

Indicators of Compromise

• Unexpected network traffic directed to /SetupCompleted
• Arbitrary code execution logs from PaperCut NG services
• Unauthorized creation of user accounts or privilege escalation

Detection Strategies

Implement network monitoring to trace unusual requests to the PaperCut server. Use anomaly detection systems to identify unauthorized access attempts reflecting the attack signature for CVE-2023-27350. SentinelOne endpoint protection can detect exploit attempts against critical application parameters.

Monitoring Recommendations

• Enable verbose logging on PaperCut NG services.
• Implement firewall rules to restrict access to PaperCut's admin interfaces.
• Use intrusion detection systems (IDS) to log and alert upon attempts to access /SetupCompleted.

How to Mitigate CVE-2023-27350

Immediate Actions Required

• Update to the latest version of PaperCut NG which includes the security patch.
• Apply network segmentation to limit access to critical resources.
• Regularly audit user permissions and roles within PaperCut NG.

Patch Information

Refer to Papercut Vendor Advisory for patch updates and implementation guidance.

Workarounds

Limit network access to PaperCut's admin interfaces to trusted hosts only, employing firewall rules and VPNs where applicable.

# Configuration example
iptables -A INPUT -p tcp --dport <papercut_port> -s <trusted_ip> -j ACCEPT
iptables -A INPUT -p tcp --dport <papercut_port> -j DROP