How severe is CVE-2021-26777?

CVE-2021-26777 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-2021-26777 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26777?

CVE-2021-26777 affects Circutor Compact Dc-s Basic Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-26777?

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-2021-26777 published?

CVE-2021-26777 was published on 2021-12-02 and last updated on 2026-06-17.

CVE-2021-26777

CVE-2021-26777 is a critical-severity vulnerability in Circutor Compact Dc-s Basic 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 2% (82nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Circutor Compact Dc-s Basic Firmware
Published: 2021-12-02
Last modified: 2026-06-17

Description

Buffer overflow vulnerability in function SetFirewall in index.cgi in CIRCUTOR COMPACT DC-S BASIC smart metering concentrator Firwmare version CIR_CDC_v1.2.17, allows attackers to execute arbitrary code.

Frequently asked questions

What is CVE-2021-26777?: Buffer overflow vulnerability in function SetFirewall in index.cgi in CIRCUTOR COMPACT DC-S BASIC smart metering concentrator Firwmare version CIR_CDC_v1.2.17, allows attackers to execute arbitrary code.
How severe is CVE-2021-26777?: CVE-2021-26777 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-2021-26777 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26777?: CVE-2021-26777 affects Circutor Compact Dc-s Basic Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-26777?: 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-2021-26777 published?: CVE-2021-26777 was published on 2021-12-02 and last updated on 2026-06-17.

References

https://github.com/Ell0/plc_concentrator_vulns/

Affected products (1)

cpe:2.3:o:circutor:compact_dc-s_basic_firmware:1.2.17:*:*:*:*:*:*:*

More vulnerabilities in Circutor Compact Dc-s Basic Firmware

CVE-2022-1669 — Medium (CVSS 6.8): A buffer overflow vulnerability has been detected in the firewall function of the device management web portal. The…

All CVEs affecting Circutor Compact Dc-s Basic Firmware →

Other CWE-120 (Classic Buffer Overflow) vulnerabilities

CVE-2025-48611 — Critical (CVSS 10.0): In DeviceId of DeviceId.java, there is a possible desync in persistence due to a missing bounds check. This could lead…
CVE-2026-24823 — Critical (CVSS 10.0): Out-of-bounds Write, Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in FASTSHIFT…
CVE-2026-24810 — Critical (CVSS 10.0): Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in rethinkdb (src/cjson modules).…
CVE-2026-24800 — Critical (CVSS 10.0): Out-of-bounds Write, Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') vulnerability in tildearrow…
CVE-2025-9962 — Critical (CVSS 10.0): A buffer overflow vulnerability in Novakon P series allows attackers to gain root permission without prior…
CVE-2010-10016 — Critical (CVSS 10.0): BS.Player version 2.57 (build 1051) contains a vulnerability in its playlist import functionality. When processing .m3u…

Browse all CWE-120 (Classic Buffer Overflow) vulnerabilities →