CVE-2026-25715: Authentication Bypass Vulnerability

CVE-2026-25715 Overview

The web management interface of the affected device contains a critical security flaw that allows administrator credentials to be configured with blank values. Once this configuration is applied, the device permits authentication with empty credentials over both the web management interface and Telnet service. This vulnerability effectively disables authentication across all critical management channels, allowing any network-adjacent attacker to gain full administrative control without providing any credentials.

Critical Impact

Complete authentication bypass enables unauthorized administrative access to device management interfaces, potentially allowing attackers to take full control of affected devices, modify configurations, and disrupt operations.

Affected Products

• Affected product information not specified in advisory
• See CISA ICS Advisory ICSA-26-050-03 for complete product details

Discovery Timeline

• February 20, 2026 - CVE-2026-25715 published to NVD
• February 20, 2026 - Last updated in NVD database

Technical Details for CVE-2026-25715

Vulnerability Analysis

This vulnerability is classified under CWE-521 (Weak Password Requirements), which occurs when the system does not enforce adequate credential policies. In this case, the web management interface fails to validate that administrator credentials meet minimum security requirements before accepting them. The system allows both the username and password fields to be set to empty strings, which fundamentally undermines the authentication mechanism.

The design flaw has severe implications for device security. When blank credentials are configured, the authentication check essentially becomes a no-op, as any authentication attempt with empty values will succeed. This affects multiple management channels simultaneously, including the web-based administration panel and the Telnet service, dramatically expanding the attack surface.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the credential management system. The device's firmware lacks proper enforcement of minimum credential requirements, allowing administrators to inadvertently or intentionally configure the device with blank authentication credentials. The absence of server-side validation checks permits this insecure configuration to persist and propagate across all authentication-dependent services.

Attack Vector

The attack vector is network-based and requires no privileges, user interaction, or complex attack chains. An attacker positioned on the same network segment can exploit this vulnerability in the following manner:

1. The attacker scans for devices exposing web management interfaces on common administrative ports
2. Upon discovering a vulnerable device configured with blank credentials, the attacker attempts authentication with empty username and password fields
3. The device accepts the blank credentials and grants full administrative access
4. With administrative control, the attacker can modify device configurations, disable security features, pivot to other network assets, or disrupt device operations

Since both the web interface and Telnet service accept blank credentials once configured, attackers have multiple avenues to compromise the device. The Telnet service is particularly concerning as it transmits data in cleartext, though in this case, there are effectively no credentials to intercept.

Detection Methods for CVE-2026-25715

Indicators of Compromise

• Successful authentication events to web management interface or Telnet service with empty or blank credential fields
• Administrative configuration changes originating from unexpected IP addresses or at unusual times
• Multiple rapid authentication attempts to management interfaces from scanning activity
• Device configuration exports or imports not initiated by authorized personnel

Detection Strategies

• Implement network monitoring to detect authentication attempts with empty credential fields to device management interfaces
• Configure alerting for any administrative login events to affected devices, especially from non-whitelisted IP addresses
• Deploy intrusion detection rules to identify Telnet traffic to device management ports from unauthorized network segments
• Audit device configurations periodically to ensure administrator credentials are properly set and meet security requirements

Monitoring Recommendations

• Enable comprehensive logging on all device management interfaces and forward logs to a centralized SIEM
• Monitor for configuration changes to authentication settings on affected devices
• Implement network segmentation monitoring to detect unauthorized access attempts to management VLANs
• Set up automated configuration compliance checks to detect devices with blank or weak credentials

How to Mitigate CVE-2026-25715

Immediate Actions Required

• Immediately audit all affected devices to verify administrator credentials are not set to blank values
• Configure strong, unique administrator passwords on all device management interfaces
• Restrict network access to management interfaces using firewall rules or VLAN segmentation
• Disable Telnet service if not required and use SSH or HTTPS for secure management access
• Implement IP whitelisting to limit management interface access to authorized administrator workstations only

Patch Information

Consult the CISA ICS Advisory ICSA-26-050-03 for vendor-specific patch and firmware update information. The GitHub CSAF JSON File contains additional technical details and remediation guidance from the vendor.

Workarounds

• Ensure administrator credentials are set to strong, complex values that meet organizational password policies
• Isolate affected devices on dedicated management networks with strict access controls
• Implement jump servers or bastion hosts as the sole authorized access points for device management
• Deploy network access control (NAC) solutions to prevent unauthorized devices from reaching management interfaces
• Monitor and alert on any authentication attempts to management interfaces until patches are applied

# Network segmentation example - restrict management interface access
# Example iptables rules for Linux-based network devices

# Allow management access only from authorized admin network
iptables -A INPUT -p tcp --dport 80 -s 10.10.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.10.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 23 -s 10.10.100.0/24 -j ACCEPT

# Drop all other management interface traffic
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
iptables -A INPUT -p tcp --dport 23 -j DROP