CVE-2021-20843: Cross-site script inclusion vulnerability in the Web GUI of RTX830 Rev.15.02.17 and earlier, NVR510 Rev.15.01.
32
Routine
MEDIUM 5.4UPGRADEUPGRADEUPGRADE
CVE-2021-20843 is a medium-severity flaw (CVSS 5.4) affecting rtx830 firmware, nvr510 firmware, nvr700w firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
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
yamaha rtx830 firmware UPGRADE
Affected: <= 15.02.17
Fixed in: newer than 15.02.17
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
yamaha nvr510 firmware UPGRADE
Affected: <= 15.01.18
Fixed in: newer than 15.01.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
yamaha nvr700w firmware UPGRADE
Affected: <= 15.00.19
Fixed in: newer than 15.00.19
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
yamaha rtx1210 firmware UPGRADE
Affected: <= 14.01.38
Fixed in: newer than 14.01.38
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
ntt-west biz box rtx830 firmware UPGRADE
Affected: <= 15.02.17
Fixed in: newer than 15.02.17
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
ntt-west biz box nvr510 firmware UPGRADE
Affected: < 15.01.18
Fixed in: 15.01.18
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official sourceNVD · CVE Program · Report a problem with this page 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-2021-20843?
rtx830 firmware: upgrade to newer than 15.02.17; nvr510 firmware: upgrade to newer than 15.01.18; nvr700w firmware: upgrade to newer than 15.00.19. Exact commands for each OS are on this page.
Is CVE-2021-20843 being exploited?
CVE-2021-20843 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-2021-20843 affect?
CVE-2021-20843 affects rtx830 firmware, nvr510 firmware, nvr700w firmware. Severity is medium (CVSS 5.4). 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 a
How urgent is CVE-2021-20843?
Priority 32/100. No elevated risk signals yet.
Related CVEs
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CVE-2020-5548HIGH 7.5UPGRADEUPGRADE Yamaha LTE VoIP Router(NVR700W firmware Rev.15.00.15 and earlier), Yamaha Gigabit VoIP Router(NVR510 firmware
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