CVE-2025-41730: Wago 0852-1328 Firmware RCE Vulnerability

CVE-2025-41730 Overview

CVE-2025-41730 is a critical stack-based buffer overflow vulnerability affecting Wago industrial managed switches. An unauthenticated remote attacker can abuse unsafe sscanf calls within the check_account() function to write arbitrary data into fixed-size stack buffers, leading to full device compromise. This vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and CWE-787 (Out-of-bounds Write).

Critical Impact

This vulnerability allows unauthenticated remote attackers to achieve full device compromise on affected Wago industrial managed switches through stack-based buffer overflow exploitation, potentially disrupting critical industrial control system operations.

Affected Products

• Wago 0852-1328 Firmware
• Wago 0852-1328 Hardware
• Wago 0852-1322 Firmware
• Wago 0852-1322 Hardware

Discovery Timeline

• 2025-12-10 - CVE-2025-41730 published to NVD
• 2025-12-19 - Last updated in NVD database

Technical Details for CVE-2025-41730

Vulnerability Analysis

This vulnerability exists in the authentication handling code of affected Wago industrial managed switch firmware. The check_account() function employs unsafe sscanf calls to parse user-supplied input without proper bounds checking. When processing authentication requests, the function writes data directly into fixed-size stack buffers without validating the length of the input data. This design flaw allows attackers to overflow the buffer boundaries, corrupting adjacent stack memory including return addresses and saved registers.

The vulnerability is particularly severe because it requires no authentication to exploit. An attacker with network access to the device can send specially crafted packets to trigger the overflow, potentially achieving arbitrary code execution with the privileges of the affected process. Given that these are industrial managed switches used in operational technology (OT) environments, successful exploitation could impact critical infrastructure operations.

Root Cause

The root cause of this vulnerability is the use of unsafe sscanf calls without proper input length validation in the check_account() function. The function allocates fixed-size stack buffers but does not restrict the amount of data that can be written into them from user-controlled input. This is a classic stack-based buffer overflow pattern that has been well-documented in security literature but continues to appear in embedded systems and firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack vector is network-based, requiring no user interaction and no privileges. An attacker can remotely target the vulnerable check_account() function by sending malicious authentication requests to the switch's management interface. The attacker crafts input that exceeds the expected buffer size, overwriting critical stack data. By carefully controlling the overflow data, the attacker can redirect program execution to attacker-controlled code, achieving full device compromise.

The exploitation mechanism follows a standard stack buffer overflow approach:

1. The attacker identifies the network service exposing the vulnerable check_account() function
2. A malicious request is crafted with input data exceeding the fixed-size stack buffer allocation
3. The unsafe sscanf call writes beyond buffer boundaries, corrupting stack memory
4. Overwritten return addresses or function pointers redirect execution to attacker-controlled code
5. The attacker achieves arbitrary code execution with the privileges of the vulnerable process

For detailed technical information, refer to the CERT-VDE Security Advisory.

Detection Methods for CVE-2025-41730

Indicators of Compromise

• Unexpected crashes or reboots of affected Wago managed switches
• Anomalous network traffic patterns targeting switch management interfaces
• Authentication service failures or unexpected behavior on affected devices
• Evidence of unauthorized configuration changes on managed switches

Detection Strategies

• Monitor network traffic for unusually large authentication requests to Wago switch management interfaces
• Implement intrusion detection rules to identify potential buffer overflow exploitation patterns
• Deploy network segmentation monitoring to detect lateral movement from compromised OT devices
• Review device logs for authentication failures and service crashes

Monitoring Recommendations

• Establish baseline network behavior for Wago managed switches and alert on deviations
• Implement continuous monitoring of OT network segments containing affected devices
• Configure SIEM rules to correlate authentication anomalies with network traffic patterns
• Enable logging on all network management interfaces for affected devices

How to Mitigate CVE-2025-41730

Immediate Actions Required

• Restrict network access to affected Wago switch management interfaces to trusted administrative hosts only
• Implement network segmentation to isolate affected devices from untrusted network segments
• Monitor for vendor firmware updates and apply patches as soon as available
• Review firewall rules to limit exposure of management interfaces

Patch Information

Organizations should monitor Wago and CERT-VDE for official firmware updates addressing this vulnerability. The CERT-VDE Security Advisory VDE-2025-095 provides authoritative information on available patches and remediation guidance. Apply firmware updates according to your organization's change management procedures, prioritizing devices with the highest exposure to untrusted networks.

Workarounds

• Disable or restrict remote management access to affected switches until patches are applied
• Place affected devices behind firewalls that filter and inspect incoming management traffic
• Implement jump servers or bastion hosts for administrative access to affected devices
• Consider enabling any available rate limiting or connection throttling features on management interfaces

# Example firewall rule to restrict management access (adjust to your environment)
# Allow management access only from trusted admin subnet
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
iptables -A INPUT -p tcp --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP