CVE-2021-27179Public exploitNetwork attack vector

Telnet service crash via malformed command sequence

Published Feb 10, 2021 · Updated Aug 3, 2024

Improper input validation in FiberHome HG6245D firmware through RP2613 allows remote attackers to crash the CLI telnet daemon. The /fh/extend/load_cli process segfaults after parsing a 13-byte Telnet sequence containing the enable command and control bytes. The service requires enablement for IPv4 access but is exposed over IPv6 by default; exploitation stops Telnet connections without rebooting the router.

CVSS severity7.5
High
EPSS probability13.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in FiberHome HG6245D firmware through RP2613 allows remote attackers to crash the CLI telnet daemon. The /fh/extend/load_cli process segfaults after parsing a 13-byte Telnet sequence containing the enable command and control bytes. The service requires enablement for IPv4 access but is exposed over IPv6 by default; exploitation stops Telnet connections without rebooting the router.

The record

CVE
CVE-2021-27179
Published
Feb 10, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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