How severe is CVE-2021-20856?

CVE-2021-20856 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-2021-20856 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20856?

CVE-2021-20856 primarily affects Elecom Wrh-733gbk Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20856?

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

When was CVE-2021-20856 published?

CVE-2021-20856 was published on 2021-12-01 and last updated on 2026-06-17.

CVE-2021-20856

CVE-2021-20856 is a medium-severity vulnerability in Elecom Wrh-733gbk 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-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Elecom Wrh-733gbk Firmware
Published: 2021-12-01
Last modified: 2026-06-17

Description

Cross-site scripting vulnerability in ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a remote authenticated attacker to inject an arbitrary script via unspecified vectors.

Frequently asked questions

What is CVE-2021-20856?: Cross-site scripting vulnerability in ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a remote authenticated attacker to inject an arbitrary script via unspecified vectors.
How severe is CVE-2021-20856?: CVE-2021-20856 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-2021-20856 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20856?: CVE-2021-20856 primarily affects Elecom Wrh-733gbk Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20856?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20856 published?: CVE-2021-20856 was published on 2021-12-01 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:elecom:wrh-733gbk_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:elecom:wrh-733gwh_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Elecom Wrh-733gbk Firmware

CVE-2021-20854 — Medium (CVSS 6.8): ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a…
CVE-2021-20853 — Medium (CVSS 6.8): ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a…
CVE-2021-20852 — Medium (CVSS 6.8): Buffer overflow vulnerability in ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware…
CVE-2021-20855 — Medium (CVSS 5.4): Cross-site scripting vulnerability in ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware…

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