CVE-2025-20333
About
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.
Rainforest analyst review
The VPN web server in Cisco Secure Firewall ASA and FTD software improperly validates user-supplied input in HTTP(S) requests. An attacker who holds valid VPN user credentials sends crafted requests that overflow a buffer, and the resulting memory corruption is steered into arbitrary code execution as root — complete compromise of the firewall itself. The credential requirement is a low bar given how routinely VPN logins are phished or reused.
This was disclosed with CVE-2025-20362 as part of the 2025 campaign against Cisco ASA appliances linked to the ArcaneDoor activity, with in-the-wild exploitation and device implants reported. These are perimeter firewalls and VPN concentrators — the exact chokepoint devices attackers most want to own, because control there means control of everything terminating behind them. Apply Cisco's fixed software urgently, and because attackers in this campaign established persistence, don't stop at patching: inspect for implants and unauthorized changes, verify image integrity, and follow Cisco's forensic guidance on affected units.
References
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Frequently asked questions
What is CVE-2025-20333?
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.
How severe is CVE-2025-20333?
CVE-2025-20333 carries a CVSS 3.1 base score of 9.9, rated critical. On the Rainforest Risk Index — which weighs the severity alongside how easy the flaw is to reach and how broad its impact is — it scores 100 out of 100, in the critical band.
How is CVE-2025-20333 exploited?
According to the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H): attack vector Network, attack complexity Low, privileges required Low, user interaction None. Impact on confidentiality High, integrity High and availability High.
Which products are affected by CVE-2025-20333?
Public advisories list the following as affected: adaptive security appliance software, secure firewall threat defense. Check the references on this page for the exact versions each vendor confirms.
How do I fix CVE-2025-20333?
Apply the fix the vendor published — the references on this page link to the primary advisories and patches. When patching can't happen right away, reduce the exposure of the affected component and watch it for exploitation attempts. Rainforest customers see this vulnerability correlated to their own assets and prioritized by real exposure, not by score alone.
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