CVE-2024-27942 Overview
CVE-2024-27942 affects Siemens RUGGEDCOM CROSSBOW in all versions prior to V5.5. The vulnerability allows any unauthenticated remote client to disconnect active users from the server. Successful exploitation produces a denial-of-service (DoS) condition that prevents legitimate users from performing operational tasks. The flaw maps to [CWE-306] Missing Authentication for Critical Function and is exploitable over the network without privileges or user interaction.
RUGGEDCOM CROSSBOW is widely deployed in industrial and utility environments for secure remote access management to substations and field assets. A reliable DoS vector against these systems can interrupt operator workflows in critical infrastructure.
Critical Impact
An unauthenticated remote attacker can repeatedly disconnect any active user from the RUGGEDCOM CROSSBOW server, disrupting operational technology (OT) management activities.
Affected Products
- Siemens RUGGEDCOM CROSSBOW: all versions prior to V5.5
- Deployments serving remote access to RUGGEDCOM and third-party OT assets
- Environments exposing the CROSSBOW server to untrusted network segments
Discovery Timeline
- 2024-05-14 - CVE-2024-27942 published to the National Vulnerability Database (NVD)
- 2024-05-14 - Siemens publishes Security Advisory SSA-916916
- 2025-02-06 - Last updated in NVD database
Technical Details for CVE-2024-27942
Vulnerability Analysis
The defect resides in the RUGGEDCOM CROSSBOW server's handling of client session control messages. The server processes a disconnect-style request without first authenticating the originating client. An attacker with network reachability to the CROSSBOW service can issue crafted requests that terminate the sessions of authenticated users.
Because the operation requires no credentials and no user interaction, it can be scripted and repeated. Each request forces target users back through the authentication workflow, blocking practical use of the platform. The vulnerability impacts availability only; confidentiality and integrity are not affected.
Root Cause
The root cause is missing authentication for a critical function [CWE-306]. The server accepts and acts on session termination requests from any client capable of reaching the service. There is no verification that the requester owns the targeted session or holds administrative authority over connected users.
Attack Vector
Exploitation occurs over the network against the CROSSBOW server's listening service. The attacker requires no account on the system and does not need to trick a user into any action. By looping the disconnect request, an attacker can sustain the denial-of-service condition indefinitely against all active operators.
No public proof-of-concept code has been released, and the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. Technical specifics are documented in Siemens Security Advisory SSA-916916.
Detection Methods for CVE-2024-27942
Indicators of Compromise
- Repeated, unexpected disconnections of CROSSBOW client sessions across multiple users
- Server-side session termination events without matching user-initiated logoff actions
- Inbound traffic to the CROSSBOW service from unexpected source IP addresses or network segments
- Operator reports of inability to maintain a stable CROSSBOW session
Detection Strategies
- Monitor CROSSBOW server logs for high-frequency session termination events that lack corresponding authenticated client activity
- Correlate disconnect events with network flow data to identify external or unauthorized source addresses
- Alert on bursts of session terminations affecting multiple distinct users within a short interval
Monitoring Recommendations
- Forward CROSSBOW application and authentication logs to a centralized SIEM for correlation and retention
- Track baseline session duration and disconnect rates; alert on statistically significant deviations
- Capture network telemetry at the perimeter of OT management networks to detect probes against the CROSSBOW service port
How to Mitigate CVE-2024-27942
Immediate Actions Required
- Upgrade RUGGEDCOM CROSSBOW to version V5.5 or later as directed by Siemens advisory SSA-916916
- Restrict network access to the CROSSBOW server using firewalls and access control lists so only authorized management hosts can reach the service
- Place CROSSBOW servers within a segmented OT management zone, isolated from general corporate networks and the internet
- Enable verbose session and authentication logging and forward logs to a monitored SIEM
Patch Information
Siemens addresses the vulnerability in RUGGEDCOM CROSSBOW V5.5. Operators should plan an upgrade following the guidance in Siemens Security Advisory SSA-916916. Validate the upgrade in a staging environment, then schedule production deployment during a controlled maintenance window.
Workarounds
- Apply strict network segmentation and limit CROSSBOW reachability to a defined set of administrative source addresses
- Front the service with a VPN or jump host that enforces authentication before any traffic reaches the CROSSBOW server
- Continuously monitor for anomalous disconnect activity and have an incident response runbook ready to block offending source addresses at the firewall
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
