CVE-2024-23811: Siemens Sinec NMS RCE Vulnerability

CVE-2024-23811 Overview

CVE-2024-23811 is an arbitrary file upload vulnerability in Siemens SINEC NMS (Network Management System). All versions prior to V2.0 SP1 accept arbitrary file uploads through the Trivial File Transfer Protocol (TFTP) service. An attacker positioned on an adjacent network can push malicious firmware images or other files to the management platform. This upload primitive can lead to remote code execution on the affected host. The weakness is classified as [CWE-434] Unrestricted Upload of File with Dangerous Type.

Critical Impact
Adjacent-network attackers can upload arbitrary files, including malicious firmware images, and potentially achieve remote code execution against a central OT network management platform.

Affected Products

Siemens SINEC NMS — all versions before V2.0 SP1
Siemens SINEC NMS V2.0 (base release)
Deployments exposing the SINEC NMS TFTP service to adjacent networks

Discovery Timeline

2024-02-13 - CVE-2024-23811 published to NVD with Siemens advisory SSA-943925
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-23811

Vulnerability Analysis

SINEC NMS is Siemens' network management platform for industrial networks. The product exposes a TFTP service used for configuration and firmware distribution to managed devices. The affected versions do not restrict which files can be written through this service. An attacker on an adjacent network segment can therefore place arbitrary payloads onto the server file system without authentication.

Because TFTP is a connectionless UDP protocol with no built-in authentication, the upload path relies entirely on server-side validation. In vulnerable SINEC NMS builds, that validation is insufficient. Attackers can write executable content, replace firmware images consumed by downstream devices, or overwrite configuration files trusted by the NMS process.

Exploitation can pivot from arbitrary write to remote code execution when a written file lands in a location processed by SINEC NMS or its managed devices. This gives the attacker code execution in the context of the management server or on industrial endpoints that later pull the poisoned firmware.

Root Cause

The root cause is missing validation of file type, destination path, and authentication state on the SINEC NMS TFTP upload handler [CWE-434]. The service treats any inbound TFTP write request as legitimate and commits the payload to disk.

Attack Vector

The attack vector is adjacent network. The attacker must reach the SINEC NMS TFTP port from a network segment routable to the management interface. No credentials and no user interaction are required. The attacker sends a TFTP write request (WRQ) referencing a chosen filename and streams the payload. See the Siemens Security Advisory SSA-943925 for vendor-specific technical details.

Detection Methods for CVE-2024-23811

Indicators of Compromise

Unexpected TFTP WRQ (write request) packets directed at the SINEC NMS server on UDP port 69
New or modified files in SINEC NMS TFTP working directories that do not correspond to scheduled operations
Firmware images on managed devices with hashes that do not match vendor-published values
SINEC NMS process spawning shells, scripting interpreters, or unexpected child processes

Detection Strategies

Inspect network flow records for inbound UDP/69 traffic to SINEC NMS from hosts other than approved administrative workstations
Enable file integrity monitoring on TFTP root directories and firmware repositories used by SINEC NMS
Alert on writes of executable extensions (.exe, .dll, .sh, .bin, firmware container formats) via TFTP

Monitoring Recommendations

Forward SINEC NMS host logs and network telemetry from the OT management VLAN to a centralized SIEM for correlation
Baseline expected TFTP client IPs and alert on deviations
Track parent-child process relationships on the SINEC NMS server to detect post-upload code execution

How to Mitigate CVE-2024-23811

Immediate Actions Required

Upgrade SINEC NMS to V2.0 SP1 or later as directed by Siemens advisory SSA-943925
Restrict TFTP access on the SINEC NMS server to a dedicated management VLAN using firewall rules
Audit the TFTP upload directory for unrecognized files and validate firmware images against vendor hashes

Patch Information

Siemens has released SINEC NMS V2.0 SP1, which addresses CVE-2024-23811. Refer to the Siemens Security Advisory SSA-943925 for the fixed version, download instructions, and additional guidance.

Workarounds

Block UDP port 69 at the perimeter of the OT management network when TFTP is not required
Place SINEC NMS behind a jump host and permit management traffic only from authenticated administrative endpoints
Segment managed industrial devices from general enterprise networks in line with IEC 62443 zone-and-conduit guidance

bash

# Configuration example: restrict TFTP (UDP/69) to trusted admin subnet on Linux iptables
iptables -A INPUT -p udp --dport 69 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 69 -j DROP