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CVE-2021-20843

20
FAUCET Score

CVE-2021-20843 is a cross-site script inclusion vulnerability affecting the Web GUI of several Yamaha and NTT-West router and NVR models, including RTX830, NVR510, NVR700W, and RTX1210. This medium-severity vulnerability (CVSS 5.4) allows a remote, authenticated attacker to alter device settings by tricking a user into visiting a specially crafted web page. While requiring user interaction and authentication, successful exploitation could lead to unauthorized configuration changes. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 15.02.17CPE matchmatch criteria
cpe:2.3:o:yamaha:rtx830_firmware:*:*:*:*:*:*:*:*
<= 15.01.18CPE matchmatch criteria
cpe:2.3:o:yamaha:nvr510_firmware:*:*:*:*:*:*:*:*
<= 15.00.19CPE matchmatch criteria
cpe:2.3:o:yamaha:nvr700w_firmware:*:*:*:*:*:*:*:*
<= 14.01.38CPE matchmatch criteria
cpe:2.3:o:yamaha:rtx1210_firmware:*:*:*:*:*:*:*:*
<= 15.02.17CPE matchmatch criteria
cpe:2.3:o:ntt-west:biz_box_rtx830_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.4MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.3
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.67%
Probability of exploitation in next 30 days
EPSS Percentile
48.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0067 is in the 81st percentile among its peer group of 15,239 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

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

Remediation

Remediation records are not available for this CVE.

References

business.ntt-east.co.jp / topics/2021/11_09.html
MitigationVendor Advisory
jvn.jp / en/vu/JVNVU91161784/index.html
MitigationThird Party Advisory
ntt-west.co.jp / smb/kiki_info/info/211109.html
MitigationVendor Advisory
rtpro.yamaha.co.jp / RT/FAQ/Security/JVNVU91161784.html
MitigationVendor Advisory