CVE-2023-50916: Kyocera Device Manager SSRF Vulnerability

CVE-2023-50916 Overview

CVE-2023-50916 is a path traversal vulnerability (CWE-22) affecting Kyocera Device Manager before version 3.1.1213.0. The vulnerability allows attackers to expose NTLM credentials through UNC path authentication by exploiting improper input validation in the backup location configuration feature. While the GUI attempts to prevent UNC paths by rejecting backslash characters, attackers can bypass this restriction by intercepting and modifying HTTP requests via a proxy or by sending requests directly to the application endpoint.

Critical Impact

Successful exploitation enables attackers to capture Windows NTLM hashes, potentially leading to credential relaying attacks or offline password cracking, compromising the entire Windows domain authentication infrastructure.

Affected Products

• Kyocera Device Manager versions prior to 3.1.1213.0
• Enterprise environments using Kyocera Device Manager for printer fleet management
• Windows environments with NTLM authentication enabled

Discovery Timeline

• 2024-01-10 - CVE-2023-50916 published to NVD
• 2025-06-03 - Last updated in NVD database

Technical Details for CVE-2023-50916

Vulnerability Analysis

This vulnerability exists in the backup configuration functionality of Kyocera Device Manager. Administrators have the ability to specify a backup location for the application's database. The application implements client-side validation that rejects paths containing backslash (\) characters, which should prevent the use of UNC paths in the format \\server\share.

However, this security control operates only at the GUI level. By intercepting the HTTP request using a proxy tool or by crafting requests directly to the backend endpoint, an attacker with administrative access can bypass this validation entirely. Once a malicious UNC path is configured, Kyocera Device Manager attempts to verify access to the specified location by authenticating to it. In Windows environments configured to use NTLM authentication, this triggers the application to send NTLM credentials to the attacker-controlled server.

The captured NTLM hashes can then be used in two primary attack scenarios: NTLM relay attacks, where the credentials are forwarded to another system to gain unauthorized access, or offline password cracking using tools like Hashcat or John the Ripper to recover plaintext passwords.

Root Cause

The root cause is insufficient server-side input validation combined with reliance on client-side security controls. The application fails to properly sanitize and validate backup path inputs at the server level, allowing UNC paths to be submitted despite GUI restrictions. Additionally, the application authenticates to user-specified network paths without implementing appropriate security controls or warnings for potentially malicious destinations.

Attack Vector

The attack requires administrative credentials to Kyocera Device Manager but can be executed remotely over the network. An attacker with admin access intercepts the backup location change request, modifies the local path to a UNC path pointing to their controlled server, and forwards the modified request. When Kyocera Device Manager attempts to access the UNC path, it automatically sends NTLM authentication credentials to the attacker's server.

The exploitation flow involves:

1. An attacker gains administrative access to Kyocera Device Manager
2. The attacker sets up a rogue SMB server or uses tools like Responder to capture NTLM hashes
3. The attacker intercepts and modifies the backup location request to specify a UNC path (e.g., \\attacker-server\share)
4. Kyocera Device Manager authenticates to the UNC path, exposing NTLM credentials
5. The attacker captures the credentials for relay or cracking attacks

For detailed technical information, refer to the Trustwave Security Advisory TWSL2024-001.

Detection Methods for CVE-2023-50916

Indicators of Compromise

• Unexpected SMB connection attempts from servers running Kyocera Device Manager to external or unusual IP addresses
• Backup configuration changes in Kyocera Device Manager logs that contain UNC paths
• Authentication events showing NTLM authentication attempts to unknown or suspicious servers
• Network traffic showing SMB traffic on ports 445 or 139 to non-standard destinations

Detection Strategies

• Monitor Kyocera Device Manager configuration changes, specifically backup location settings, for UNC path entries
• Implement network monitoring to detect outbound SMB connections from servers hosting Kyocera Device Manager
• Review Windows Security event logs for NTLM authentication events (Event ID 4624, 4648) involving the Kyocera Device Manager service account
• Deploy endpoint detection rules to alert on configuration file modifications in the Kyocera Device Manager installation directory

Monitoring Recommendations

• Configure SIEM rules to correlate Kyocera Device Manager administrative actions with unusual network activity
• Implement egress filtering to restrict SMB traffic from application servers to authorized destinations only
• Enable enhanced logging on Kyocera Device Manager to capture all administrative configuration changes
• Monitor for the use of proxy tools or API manipulation targeting Kyocera Device Manager endpoints

How to Mitigate CVE-2023-50916

Immediate Actions Required

• Upgrade Kyocera Device Manager to version 3.1.1213.0 or later immediately
• Audit current backup location configurations to ensure no UNC paths have been set
• Review access logs for any suspicious administrative activity or configuration changes
• Restrict administrative access to Kyocera Device Manager to only essential personnel
• Implement network segmentation to limit SMB traffic from Kyocera Device Manager servers

Patch Information

Kyocera has released version 3.1.1213.0 of Device Manager that addresses this vulnerability by implementing proper server-side validation of backup paths. Organizations should prioritize upgrading to this version or later. For detailed patch information and upgrade instructions, refer to the Kyocera Security Advisory.

Workarounds

• Block outbound SMB traffic (ports 445 and 139) from servers running Kyocera Device Manager using host-based or network firewalls
• Disable NTLM authentication where possible and enforce Kerberos-only authentication in the Windows environment
• Implement web application firewall rules to block requests containing UNC path patterns to the Kyocera Device Manager application
• Use network segmentation to isolate Kyocera Device Manager from untrusted networks

# Windows Firewall rule to block outbound SMB from Kyocera Device Manager server
netsh advfirewall firewall add rule name="Block Outbound SMB" dir=out action=block protocol=tcp localport=445
netsh advfirewall firewall add rule name="Block Outbound NetBIOS" dir=out action=block protocol=tcp localport=139