CVE-2026-2533: Tosei Washing Machine RCE Vulnerability

CVE-2026-2533 Overview

A command injection vulnerability has been identified in Tosei Self-service Washing Machine firmware version 4.02. The flaw exists in an unknown function within the file /cgi-bin/tosei_datasend.php, where manipulation of the adr_txt_1 argument can lead to arbitrary command injection. This vulnerability is remotely exploitable without authentication, potentially allowing attackers to execute malicious commands on the affected IoT device.

Critical Impact

Remote attackers can exploit this command injection vulnerability to execute arbitrary system commands on Tosei Self-service Washing Machine devices, potentially compromising device integrity, stealing sensitive data, or using the device as a pivot point for further network attacks.

Affected Products

• Tosei Self-service Washing Machine firmware version 4.02

Discovery Timeline

• 2026-02-16 - CVE CVE-2026-2533 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-2533

Vulnerability Analysis

This vulnerability falls under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as injection vulnerabilities. The affected component /cgi-bin/tosei_datasend.php fails to properly sanitize user-controlled input passed through the adr_txt_1 parameter before using it in system-level operations. This allows an attacker to inject malicious commands that are then executed in the context of the web server process.

The network-accessible nature of this vulnerability significantly increases its risk profile, as attackers can exploit it remotely without requiring local access to the device. IoT devices such as self-service washing machines often operate with elevated privileges and may lack robust security controls, making successful exploitation particularly impactful.

Root Cause

The root cause of this vulnerability is improper input validation and sanitization in the tosei_datasend.php CGI script. The adr_txt_1 parameter is processed without adequate filtering of shell metacharacters or command separators, allowing attackers to break out of the intended command context and inject arbitrary commands. This is a classic example of insufficient input validation in web-accessible interfaces on embedded systems.

Attack Vector

The attack is conducted remotely over the network by sending specially crafted HTTP requests to the vulnerable CGI endpoint. An attacker can manipulate the adr_txt_1 parameter by appending shell metacharacters (such as ;, |, &&, or backticks) followed by malicious commands.

For example, an attacker might inject commands by sending a request where the adr_txt_1 parameter contains payload separators followed by system commands. The vulnerable script then passes this unsanitized input to a shell interpreter, resulting in command execution.

The exploit has been publicly disclosed and documented, increasing the likelihood of active exploitation attempts against unpatched devices. Technical details are available through the Yuque Security Analysis and VulDB entry.

Detection Methods for CVE-2026-2533

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/tosei_datasend.php containing shell metacharacters in the adr_txt_1 parameter
• Unexpected outbound network connections from Tosei washing machine devices
• Abnormal process spawning or command execution patterns on IoT devices
• Log entries showing requests with encoded command injection payloads targeting CGI endpoints

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing command injection patterns in the adr_txt_1 parameter
• Deploy network intrusion detection systems (IDS) with signatures for common command injection payloads
• Monitor HTTP access logs for suspicious requests to /cgi-bin/tosei_datasend.php with unusual parameter values
• Use behavioral analysis to detect anomalous network traffic originating from IoT devices

Monitoring Recommendations

• Enable comprehensive logging on network perimeter devices monitoring traffic to/from IoT segments
• Implement network segmentation to isolate IoT devices and monitor cross-segment communication
• Deploy endpoint detection and response (EDR) solutions capable of monitoring embedded Linux systems where feasible
• Establish baseline network behavior for IoT devices and alert on deviations

How to Mitigate CVE-2026-2533

Immediate Actions Required

• Isolate affected Tosei Self-service Washing Machine devices from untrusted networks immediately
• Implement network access controls to restrict access to the device's web interface to authorized management stations only
• Deploy WAF rules to filter malicious payloads targeting the /cgi-bin/tosei_datasend.php endpoint
• Monitor network traffic for exploitation attempts and potential compromise indicators

Patch Information

At the time of publication, the vendor (Tosei) has not responded to disclosure attempts and no official patch is available. Organizations should implement the recommended workarounds and network-level mitigations until an official security update is released. Monitor vendor communications and security advisories for patch availability.

For additional technical details, refer to the VulDB entry #346121 and the VulDB submission.

Workarounds

• Place affected devices behind a firewall and restrict access to the management interface to trusted IP addresses only
• Implement network segmentation to isolate IoT devices from critical network infrastructure
• Deploy a reverse proxy with input validation to filter malicious requests before they reach the device
• Consider disabling remote management access entirely if not required for operations
• Monitor for and block outbound connections from IoT devices to unexpected destinations

# Example firewall rule to restrict access to the vulnerable endpoint
# Allow only management network access to the CGI interface
iptables -A INPUT -p tcp --dport 80 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

# Alternative: Block specific vulnerable endpoint if device allows it
# This would require a reverse proxy configuration