PatchTheCVECVE-2021-31642: A denial of service condition exists after an integer overflow in several IoT devices from CHIYU Technology, i
CVE-2021-31642 is a medium-severity flaw (CVSS 6.5) affecting semac s2 firmware, semac d1 firmware, semac d2 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
A denial of service condition exists after an integer overflow in several IoT devices from CHIYU Technology, including BIOSENSE, Webpass, and BF-630, BF-631, and SEMAC. The vulnerability can be explored by sending an unexpected integer (> 32 bits) on the page parameter that will crash the web portal and making it unavailable until a reboot of the device.
Why this priority
- EPSS top 1%: very likely to be exploited
- Public exploit reference
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 6.5 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | Low |
| User interaction | None |
| EPSS exploit chance | 43.7% (top 1%) |
| CISA exploited list | No |
| Weakness | CWE-190 |
| Published | 2021-06-01 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Exploit-DB: CHIYU IoT Devices - Denial of Service (DoS)
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-31642?
semac s2 firmware: mitigate or apply the listed mitigation; semac d1 firmware: mitigate or apply the listed mitigation; semac d2 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-31642 being exploited?
CVE-2021-31642 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-31642 affect?
CVE-2021-31642 affects semac s2 firmware, semac d1 firmware, semac d2 firmware. Severity is medium (CVSS 6.5). A denial of service condition exists after an integer overflow in several IoT devices from CHIYU Technology, including BIOSENSE, Webpass, and BF-630, BF-631, and SEMAC. The vulnerability can be explored by sending an unexpected integer (> 3
How urgent is CVE-2021-31642?
Priority 52/100. EPSS top 1%: very likely to be exploited; Public exploit reference
Related CVEs
- CVE-2021-31643 MEDIUM 5.4 MITIGATE MITIGATE An XSS vulnerability exists in several IoT devices from CHIYU Technology, including SEMAC, Biosense, BF-630, B
- CVE-2021-31641 MEDIUM 6.1 MITIGATE MITIGATE An unauthenticated XSS vulnerability exists in several IoT devices from CHIYU Technology, including BF-630, BF
- CVE-2021-31252 MEDIUM 6.1 MITIGATE MITIGATE An open redirect vulnerability exists in BF-630, BF-450M, BF-430, BF-431, BF631-W, BF830-W, Webpass, and SEMAC
- CVE-2021-31251 CRITICAL 9.8 MITIGATE MITIGATE An authentication bypass in telnet server in BF-430 and BF431 232/422 TCP/IP Converter, BF-450M and SEMAC from