{"id":"CVE-2021-31251","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-31251","generatedAt":"2026-11-05T01:22:14.347Z","title":"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…","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.","published":"2021-06-04T21:15:08.000Z","lastModified":"2026-06-17T03:51:30.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-287"],"affected":["chiyu-tech/bf-430 firmware","chiyu-tech/bf-431 firmware","chiyu-tech/bf-450m firmware","chiyu-tech/semac s2 firmware","chiyu-tech/semac d1 firmware","chiyu-tech/semac d2 firmware","chiyu-tech/semac d4 firmware","chiyu-tech/semac s3v3 firmware","chiyu-tech/semac d2 n300 firmware","chiyu-tech/semac s1 osdp firmware"],"epss":{"score":0.35714,"percentile":0.98464,"date":"2026-11-03","history":[]},"kev":{"listed":false},"exploits":{"count":1,"verified":false,"firstPublished":"2021-06-03","source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[{"edbId":49936,"kind":"exploit","title":"CHIYU IoT Devices - 'Telnet' Authentication Bypass","url":"https://www.exploit-db.com/exploits/49936","sourceUrl":"https://gitlab.com/exploit-database/exploitdb/-/blob/main/exploits/hardware/remote/49936.py","file":"exploits/hardware/remote/49936.py","published":"2021-06-03","added":"2021-06-03","updated":"2021-06-03","author":"sirpedrotavares","type":"remote","platform":"hardware","port":null,"verified":false,"codes":["CVE-2021-31251"],"tags":null,"aliases":null,"applicationUrl":null,"screenshotUrl":null,"referenceUrl":null}]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 35.7%, higher than 98% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"https://gitbook.seguranca-informatica.pt/cve-and-exploits/cves/chiyu-iot-devices#cve-2021-31251","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://seguranca-informatica.pt/dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks/#.YLqK1KhKguU","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://www.chiyu-tech.com/msg/message-Firmware-update-87.html","tags":["Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://gitbook.seguranca-informatica.pt/cve-and-exploits/cves/chiyu-iot-devices#cve-2021-31251","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://seguranca-informatica.pt/dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks/#.YLqK1KhKguU","tags":["Exploit","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.chiyu-tech.com/msg/message-Firmware-update-87.html","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-31251","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}