How severe is CVE-2021-20843?

CVE-2021-20843 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-20843 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20843?

CVE-2021-20843 primarily affects Yamaha Rtx830 Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20843?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20843 published?

CVE-2021-20843 was published on 2021-11-24 and last updated on 2026-06-17.

CVE-2021-20843

CVE-2021-20843 is a medium-severity vulnerability in Yamaha Rtx830 Firmware with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-829.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-829
Affected product: Yamaha Rtx830 Firmware
Published: 2021-11-24
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-20843?: 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.
How severe is CVE-2021-20843?: CVE-2021-20843 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-20843 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20843?: CVE-2021-20843 primarily affects Yamaha Rtx830 Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20843?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20843 published?: CVE-2021-20843 was published on 2021-11-24 and last updated on 2026-06-17.

References

Affected products (8)

cpe:2.3:o:yamaha:rtx830_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:yamaha:nvr510_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:yamaha:nvr700w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:yamaha:rtx1210_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:ntt-west:biz_box_rtx830_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:ntt-west:biz_box_nvr510_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:ntt-west:biz_box_nvr700w_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:ntt-west:biz_box_rtx1210_firmware:*:*:*:*:*:*:*:*

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