CVE-2025-27456 Overview
CVE-2025-27456 is a critical authentication vulnerability affecting the Endress MEAC300-FNADE4 firmware. The SMB server's login mechanism does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame, making it susceptible to brute-force attacks. This weakness (CWE-307: Improper Restriction of Excessive Authentication Attempts) allows remote attackers to systematically guess credentials without any rate limiting or account lockout protections.
Critical Impact
Remote attackers can perform unlimited brute-force authentication attempts against the SMB server, potentially gaining unauthorized access to sensitive industrial control systems with full confidentiality, integrity, and availability impact.
Affected Products
- Endress MEAC300-FNADE4 Firmware (all versions)
- Endress MEAC300-FNADE4 Hardware Device
Discovery Timeline
- 2025-07-03 - CVE-2025-27456 published to NVD
- 2026-02-06 - Last updated in NVD database
Technical Details for CVE-2025-27456
Vulnerability Analysis
This vulnerability exists in the SMB (Server Message Block) authentication implementation of the Endress MEAC300-FNADE4 firmware. The core issue is the absence of defensive mechanisms typically employed to thwart credential guessing attacks. Without account lockout policies, login attempt delays, or IP-based rate limiting, the SMB server allows unlimited authentication requests from any network source.
The vulnerability is exploitable remotely over the network without requiring any prior authentication or user interaction. An attacker with network access to the affected device can automate password guessing attacks using common tools and wordlists. Successful exploitation would grant the attacker authenticated access to the SMB share, potentially exposing configuration files, operational data, or enabling further lateral movement within industrial control environments.
Root Cause
The root cause of CVE-2025-27456 is the improper implementation of authentication controls in the SMB server component. The firmware developers did not include protective mechanisms such as:
- Account lockout after a threshold of failed attempts
- Progressive delays between authentication attempts
- Connection rate limiting per source IP
- CAPTCHA or challenge-response mechanisms
This oversight allows attackers to enumerate credentials at machine speed without triggering any defensive responses from the system.
Attack Vector
The attack vector is network-based, requiring the attacker to have connectivity to the SMB service (typically TCP port 445) on the vulnerable Endress MEAC300-FNADE4 device. The attack sequence involves:
- Network reconnaissance to identify exposed SMB services on MEAC300-FNADE4 devices
- Enumeration of valid usernames if user enumeration is also possible
- Automated brute-force attacks using credential lists or dictionary attacks
- Successful authentication with compromised credentials
- Access to SMB shares and potential pivoting within the ICS environment
The vulnerability affects industrial equipment, making it particularly concerning for operational technology (OT) environments where unauthorized access could impact physical processes.
Detection Methods for CVE-2025-27456
Indicators of Compromise
- Unusually high volume of SMB authentication failures from single or multiple source IPs
- Rapid successive login attempts to the MEAC300-FNADE4 device
- Authentication logs showing systematic username enumeration patterns
- Successful authentication after extended periods of failed attempts from the same source
Detection Strategies
- Configure network monitoring to alert on excessive SMB authentication traffic to industrial devices
- Implement log aggregation and analysis for authentication events on MEAC300-FNADE4 devices
- Deploy network intrusion detection rules for SMB brute-force patterns
- Monitor for unusual access patterns following successful authentication on previously targeted devices
Monitoring Recommendations
- Enable verbose logging on the MEAC300-FNADE4 device if supported by firmware
- Forward authentication logs to a centralized SIEM for correlation analysis
- Establish baseline authentication patterns and alert on deviations
- Implement network flow analysis to detect anomalous SMB traffic volumes
How to Mitigate CVE-2025-27456
Immediate Actions Required
- Restrict network access to the SMB service using firewall rules or network segmentation
- Implement strong, complex passwords on all accounts with SMB access
- Place affected devices behind VPN or zero-trust network access controls
- Disable SMB service if not required for operational purposes
- Monitor authentication logs for signs of ongoing brute-force attempts
Patch Information
Consult the vendor security advisories for firmware updates that address this vulnerability. The SICK PSIRT Information page provides official security guidance. Additionally, the SICK CSAF PDF Advisory contains detailed remediation information. Organizations should also review CISA ICS Best Practices for securing industrial control systems.
Workarounds
- Implement network-level access controls to restrict SMB connectivity to authorized management stations only
- Deploy an external authentication proxy or jump host that enforces rate limiting before traffic reaches the device
- Configure network-based intrusion prevention systems to block IPs exhibiting brute-force behavior
- Segment the affected device onto an isolated network with strict ingress/egress controls
# Example firewall rule to restrict SMB access (Linux iptables)
# Allow SMB only from trusted management network
iptables -A INPUT -p tcp --dport 445 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 445 -j DROP
# Enable logging for blocked SMB attempts
iptables -A INPUT -p tcp --dport 445 -j LOG --log-prefix "SMB-BLOCKED: "
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
