CVE-2021-20989Public exploitNetwork attack vector

Session hijacking via disabled SSH host-key checks

Published Apr 19, 2021 · Updated Sep 17, 2024

Improper SSH host-key validation in Fibaro Home Center 2 and Lite firmware 4.600 and earlier allows attackers to intercept cloud tunnels. The RemoteAccess script and remote-support.lua invoke Dropbear SSH with the -y option, accepting unknown host keys before opening reverse forwards to local ports 80 or 22. An attacker able to spoof DNS or otherwise intercept the outbound connection can expose the HTTP management interface and hijack sessions, tokens, or passwords; further actions require management credentials.

CVSS severity5.9
Medium
EPSS probability1.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper SSH host-key validation in Fibaro Home Center 2 and Lite firmware 4.600 and earlier allows attackers to intercept cloud tunnels. The RemoteAccess script and remote-support.lua invoke Dropbear SSH with the -y option, accepting unknown host keys before opening reverse forwards to local ports 80 or 22. An attacker able to spoof DNS or otherwise intercept the outbound connection can expose the HTTP management interface and hijack sessions, tokens, or passwords; further actions require management credentials.

The record

CVE
CVE-2021-20989
Published
Apr 19, 2021
Updated
Sep 17, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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

5.9CERT VDECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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