What’s Vulnerable › Vulnerabilities

CVE-2021-31251

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 35.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-06-04 · updated 2026-06-17
• Weakness: CWE-287

Description

An authentication bypass in telnet server in BF-430 and BF431 232/422 TCP/IP Converter, BF-450M and SEMAC from CHIYU Technology Inc allows obtaining a privileged connection with the target device by supplying a specially malformed request and an attacker may force the remote telnet server to believe that the user has already authenticated.

Affected products

• Chiyu-Tech Bf-430 Firmware: all versions
• Chiyu-Tech Bf-431 Firmware: all versions
• Chiyu-Tech Bf-450M Firmware: all versions
• Chiyu-Tech Semac D1 Firmware: all versions
• Chiyu-Tech Semac D2 Firmware: all versions
• Chiyu-Tech Semac D2 N300 Firmware: all versions
• Chiyu-Tech Semac D4 Firmware: all versions
• Chiyu-Tech Semac S1 Osdp Firmware: all versions
• Chiyu-Tech Semac S2 Firmware: all versions
• Chiyu-Tech Semac S3V3 Firmware: all versions

References

• https://gitbook.seguranca-informatica.pt/cve-and-exploits/cves/chiyu-iot-devices#cve-2021-31251
• https://seguranca-informatica.pt/dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks/#.YLqK1KhKguU
• https://www.chiyu-tech.com/msg/message-Firmware-update-87.html
• https://gitbook.seguranca-informatica.pt/cve-and-exploits/cves/chiyu-iot-devices#cve-2021-31251
• https://seguranca-informatica.pt/dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks/#.YLqK1KhKguU
• https://www.chiyu-tech.com/msg/message-Firmware-update-87.html

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