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CVE-2021-31251

59
FAUCET Score

CVE-2021-31251 is a critical authentication bypass vulnerability affecting the telnet server in various CHIYU Technology Inc. devices, including BF-430, BF431, BF-450M, and SEMAC. An unauthenticated attacker can achieve a privileged connection by sending a specially crafted request, tricking the telnet server into believing authentication has already occurred. This vulnerability carries a CVSS score of 9.8 (Critical) due to its network-based attack vector, low attack complexity, and high impact on confidentiality, integrity, and availability. While not listed on the KEV catalog, public exploit code exists (ExploitDB-49936), yet there is minimal community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:chiyu-tech:bf-430_firmware:-:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:chiyu-tech:bf-431_firmware:-:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:chiyu-tech:bf-450m_firmware:-:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:chiyu-tech:semac_s2_firmware:-:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:o:chiyu-tech:semac_d1_firmware:-:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
35.71%
Probability of exploitation in next 30 days
EPSS Percentile
98.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
ExploitDB: EDB-49936 · Jun 3, 2021
This CVE's current EPSS score of 0.3571 is in the 96th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

gitbook.seguranca-informatica.pt / cve-and-exploits/cves/chiyu-iot-devices
ExploitThird Party Advisory
seguranca-informatica.pt / dancing-in-the-iot-chiyu-devices-vulnerable-to-remote-attacks
ExploitThird Party Advisory
chiyu-tech.com / msg/message-Firmware-update-87.html
Vendor Advisory