CVE-2026-27650: Buffalo WCR-1166DHPL Firmware RCE Flaw

CVE-2026-27650 Overview

CVE-2026-27650 is an OS Command Injection vulnerability affecting a wide range of BUFFALO Wi-Fi router products. This vulnerability allows attackers to execute arbitrary operating system commands on affected devices, potentially leading to complete device compromise, network infiltration, and unauthorized access to connected systems.

OS Command Injection vulnerabilities in network infrastructure devices like routers are particularly dangerous because these devices often serve as the gateway between internal networks and the internet. Successful exploitation could allow attackers to intercept network traffic, pivot to internal systems, deploy persistent backdoors, or use the compromised router as part of a botnet.

Critical Impact

Successful exploitation enables arbitrary OS command execution on vulnerable BUFFALO routers, potentially compromising entire network segments and all connected devices.

Affected Products

• BUFFALO WCR-1166DHPL (Consumer Wi-Fi Router)
• BUFFALO WXR Series (WXR-1750DHP, WXR-1900DHP, WXR-1900DHP2, WXR-1900DHP3, WXR-5950AX12, WXR-6000AX12B/P/S, WXR18000BE10P)
• BUFFALO WZR Series (WZR-600DHP, WZR-900DHP, WZR-1166DHP, WZR-1750DHP, and variants)
• BUFFALO WSR Series (WSR3600BE4-KH, WSR3600BE4P)
• BUFFALO WRM/WTR Series Mesh Routers (WRM-D2133HP/HS, WTR-M2133HP/HS)
• BUFFALO WAPM Series Access Points (WAPM-1266R, WAPM-1750D, WAPM-2133R/TR, WAPM-AX4R/AX8R/AXETR)
• BUFFALO Enterprise/Business Products (VR-U300W, VR-U500X, WEM-1266, WAPS-1266, WAPS-AX4, FS-M1266, FS-S1266)

Discovery Timeline

• 2026-03-27 - CVE-2026-27650 published to NVD
• 2026-03-31 - Last updated in NVD database

Technical Details for CVE-2026-27650

Vulnerability Analysis

This vulnerability is classified as CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'). The flaw exists in the firmware of affected BUFFALO Wi-Fi routers and access points, where user-supplied input is passed to system command execution functions without proper sanitization or validation.

The attack requires network access to the vulnerable device and user interaction, meaning an attacker would need to convince a user to perform a specific action (such as clicking a malicious link or visiting a crafted webpage while authenticated to the router's management interface). Once exploited, the attacker gains the ability to execute arbitrary commands with the privileges of the web server process, which on embedded devices typically runs with root or administrative privileges.

The impact of successful exploitation includes complete confidentiality, integrity, and availability compromise of the affected device. Attackers could extract configuration data including Wi-Fi credentials, modify routing rules to redirect traffic, disable security features, or install persistent malware on the device firmware.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and sanitization in the router's web management interface. When processing certain user-controllable parameters, the firmware passes this input directly to shell command execution functions (such as system(), popen(), or similar) without properly escaping or filtering shell metacharacters.

This allows attackers to inject additional commands using techniques such as command chaining operators (;, &&, ||), command substitution ($(), backticks), or pipe operators (|). The firmware fails to implement proper input validation whitelisting or output encoding that would prevent these injection attacks.

Attack Vector

The attack vector for CVE-2026-27650 is network-based, requiring the attacker to have network access to the vulnerable router's management interface. The vulnerability can be exploited remotely without requiring authentication in some scenarios, though user interaction is required.

A typical attack scenario involves:

1. The attacker identifies a vulnerable BUFFALO router exposed to the network
2. The attacker crafts a malicious request containing injected OS commands within vulnerable parameters
3. Through social engineering or cross-site request forgery, the attacker tricks an authenticated administrator into triggering the malicious request
4. The router's firmware processes the request and executes the injected commands with elevated privileges
5. The attacker gains remote command execution on the device

The vulnerability affects the device's web-based administration interface. Exploitation techniques may involve embedding malicious payloads in HTTP request parameters, form fields, or URL paths that are processed by vulnerable CGI scripts or server-side handlers.

Detection Methods for CVE-2026-27650

Indicators of Compromise

• Unusual outbound connections from the router to unknown external IP addresses or command-and-control servers
• Unexpected changes to router configuration, DNS settings, or firewall rules
• New or modified files in the router's filesystem, particularly in /tmp, /var, or persistent storage areas
• Anomalous processes running on the router that are not part of standard firmware operations
• Evidence of shell commands in web server access logs containing metacharacters like ;, |, &&, or $()

Detection Strategies

• Monitor router access logs for HTTP requests containing shell metacharacters or suspicious command patterns in parameters
• Implement network traffic analysis to detect unusual data exfiltration or communication patterns from network devices
• Deploy intrusion detection signatures that identify OS command injection patterns targeting web interfaces
• Regularly audit router configurations for unauthorized changes using automated configuration management tools

Monitoring Recommendations

• Enable and centralize logging from BUFFALO router devices to a security information and event management (SIEM) system
• Configure alerts for administrative access from unexpected IP addresses or during unusual hours
• Monitor for firmware modification attempts or unauthorized access to device management interfaces
• Implement network segmentation to limit the blast radius if a router is compromised and monitor cross-segment traffic anomalies

How to Mitigate CVE-2026-27650

Immediate Actions Required

• Apply the latest firmware updates from BUFFALO immediately for all affected router models
• Restrict access to router management interfaces to trusted IP addresses only using access control lists
• Disable remote management features (WAN-side administration) if not absolutely required
• Change default administrative credentials and use strong, unique passwords for router management
• Enable HTTPS for router administration and disable HTTP access where supported

Patch Information

BUFFALO has released security updates addressing this vulnerability. Organizations should consult the Buffalo Security Advisory for the complete list of affected models and corresponding firmware versions that remediate this issue. Additionally, the JVN Vulnerability Report provides technical details and coordination information.

Firmware updates should be downloaded only from official BUFFALO sources to ensure authenticity. Verify firmware checksums when available before applying updates.

Workarounds

• Isolate affected routers on a separate network segment with strict access controls until patches can be applied
• Implement a web application firewall (WAF) or reverse proxy in front of router management interfaces to filter malicious requests
• Disable any unnecessary services or features on the router that may expose additional attack surface
• Consider replacing end-of-life devices that may no longer receive security updates with supported models

# Example: Restrict management interface access (implementation varies by model)
# Access router CLI or web interface to configure:
# 1. Disable WAN-side management access
# 2. Limit LAN management to specific IP addresses
# 3. Enable HTTPS-only administration

# Network-level mitigation using firewall rules (upstream firewall)
# Block external access to router management ports
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 8080 -j DROP