How severe is CVE-2021-27177?

CVE-2021-27177 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-2021-27177 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 20% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27177?

CVE-2021-27177 affects Fiberhome Hg6245d Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27177?

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-2021-27177 published?

CVE-2021-27177 was published on 2021-02-10 and last updated on 2026-06-17.

CVE-2021-27177

CVE-2021-27177 is a critical-severity vulnerability in Fiberhome Hg6245d Firmware with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 20% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-863.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 20% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Fiberhome Hg6245d Firmware
Published: 2021-02-10
Last modified: 2026-06-17

Description

An issue was discovered on FiberHome HG6245D devices through RP2613. It is possible to bypass authentication by sending the decoded value of the GgpoZWxwCmxpc3QKd2hvCg== string to the telnet server.

Frequently asked questions

What is CVE-2021-27177?: An issue was discovered on FiberHome HG6245D devices through RP2613. It is possible to bypass authentication by sending the decoded value of the GgpoZWxwCmxpc3QKd2hvCg== string to the telnet server.
How severe is CVE-2021-27177?: CVE-2021-27177 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-2021-27177 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 20% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27177?: CVE-2021-27177 affects Fiberhome Hg6245d Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27177?: 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-2021-27177 published?: CVE-2021-27177 was published on 2021-02-10 and last updated on 2026-06-17.

References

https://pierrekim.github.io/blog/2021-01-12-fiberhome-ont-0day-vulnerabilities.html#telnet-cli-auth-bypass

Affected products (1)

cpe:2.3:o:fiberhome:hg6245d_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Fiberhome Hg6245d Firmware

CVE-2021-27172 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. A hardcoded GEPON password for root is defined…
CVE-2021-27171 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. It is possible to start a Linux telnetd as root on…
CVE-2021-27170 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. By default, there are no firewall rules for IPv6…
CVE-2021-27168 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. There is a 6GFJdY4aAuUKJjdtSn7d password for the…
CVE-2021-27167 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. There is a password of four hexadecimal characters…
CVE-2021-27166 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. The password for the enable command is gpon.

All CVEs affecting Fiberhome Hg6245d Firmware →

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Browse all CWE-863 (Incorrect Authorization) vulnerabilities →