How severe is CVE-2021-27171?

CVE-2021-27171 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-2021-27171 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 18% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27171?

CVE-2021-27171 affects Fiberhome Hg6245d Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27171?

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-2021-27171 published?

CVE-2021-27171 was published on 2021-02-10 and last updated on 2026-06-17.

CVE-2021-27171

CVE-2021-27171 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 18% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 18% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
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 start a Linux telnetd as root on port 26/tcp by using the CLI interface commands of ddd and shell (or tshell).

Frequently asked questions

What is CVE-2021-27171?: An issue was discovered on FiberHome HG6245D devices through RP2613. It is possible to start a Linux telnetd as root on port 26/tcp by using the CLI interface commands of ddd and shell (or tshell).
How severe is CVE-2021-27171?: CVE-2021-27171 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-2021-27171 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 18% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27171?: CVE-2021-27171 affects Fiberhome Hg6245d Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27171?: 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-2021-27171 published?: CVE-2021-27171 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-privilege-escalation

Affected products (1)

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

More vulnerabilities in Fiberhome Hg6245d Firmware

CVE-2021-27177 — Critical (CVSS 9.8): An issue was discovered on FiberHome HG6245D devices through RP2613. It is possible to bypass authentication by sending…
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-2021-27170 — 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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