CVE-2021-20843

Name: CVE-2021-20843
Creator: NVD / NIST
Published: 2021-11-24T16:15:13.23+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.67%

Last modified Jun 17, 2026

CVE-2021-20843 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. Cross-site script inclusion vulnerability in the Web GUI of RTX830 Rev.15.02.17 and earlier, NVR510 Rev.15.01.18 and earlier, NVR700W Rev.15.00.19 and earlier, and RTX1210 Rev.14.01.38 and earlier allows a remote authenticated attacker to alter the settings of the product via a specially crafted web page.. EPSS estimates a 0.67% chance of exploitation in the next 30 days.

Description

Cross-site script inclusion vulnerability in the Web GUI of RTX830 Rev.15.02.17 and earlier, NVR510 Rev.15.01.18 and earlier, NVR700W Rev.15.00.19 and earlier, and RTX1210 Rev.14.01.38 and earlier allows a remote authenticated attacker to alter the settings of the product via a specially crafted web page.

Metrics

CVSS 3.1

5.4/10

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

EPSS Probability

0.67%

47.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-829

Affected Software

Vendor	Product	Versions
Yamaha	Rtx830 Firmware	<= 15.02.17
Yamaha	Nvr510 Firmware	<= 15.01.18
Yamaha	Nvr700w Firmware	<= 15.00.19
Yamaha	Rtx1210 Firmware	<= 14.01.38
Ntt-West	Biz Box Rtx830 Firmware	<= 15.02.17
Ntt-West	Biz Box Nvr510 Firmware	< 15.01.18
Ntt-West	Biz Box Nvr700w Firmware	<= 15.00.19
Ntt-West	Biz Box Rtx1210 Firmware	<= 14.01.38

References

http://www.rtpro.yamaha.co.jp/RT/FAQ/Security/JVNVU91161784.htmlMitigation, Vendor Advisory
https://business.ntt-east.co.jp/topics/2021/11_09.htmlMitigation, Vendor Advisory
https://jvn.jp/en/vu/JVNVU91161784/index.htmlMitigation, Third Party Advisory
https://www.ntt-west.co.jp/smb/kiki_info/info/211109.htmlMitigation, Vendor Advisory
http://www.rtpro.yamaha.co.jp/RT/FAQ/Security/JVNVU91161784.htmlMitigation, Vendor Advisory
https://business.ntt-east.co.jp/topics/2021/11_09.htmlMitigation, Vendor Advisory
https://jvn.jp/en/vu/JVNVU91161784/index.htmlMitigation, Third Party Advisory
https://www.ntt-west.co.jp/smb/kiki_info/info/211109.htmlMitigation, Vendor Advisory

Timeline

Published: Nov 24, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20843?

How severe is CVE-2021-20843?

CVE-2021-20843 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.67% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20843?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20843?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST