How severe is CVE-2021-20776?

CVE-2021-20776 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-20776 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20776?

CVE-2021-20776 primarily affects A-stage-inc At-40cm01sr 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-2021-20776?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-20776 published?

CVE-2021-20776 was published on 2021-07-07 and last updated on 2026-06-17.

CVE-2021-20776

CVE-2021-20776 is a critical-severity vulnerability in A-stage-inc At-40cm01sr Firmware with a CVSS 3.x base score of 9.8. 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-287.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: A-stage-inc At-40cm01sr Firmware
Published: 2021-07-07
Last modified: 2026-06-17

Description

Improper authentication vulnerability in SCT-40CM01SR and AT-40CM01SR allows an attacker to bypass access restriction and execute an arbitrary command via telnet.

Frequently asked questions

What is CVE-2021-20776?: Improper authentication vulnerability in SCT-40CM01SR and AT-40CM01SR allows an attacker to bypass access restriction and execute an arbitrary command via telnet.
How severe is CVE-2021-20776?: CVE-2021-20776 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-20776 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20776?: CVE-2021-20776 primarily affects A-stage-inc At-40cm01sr 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-2021-20776?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-20776 published?: CVE-2021-20776 was published on 2021-07-07 and last updated on 2026-06-17.

References

https://jvn.jp/en/jp/JVN21636825/index.html

Affected products (2)

cpe:2.3:o:a-stage-inc:at-40cm01sr_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:a-stage-inc:sct-40cm01sr_firmware:-:*:*:*:*:*:*:*

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