Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability
Cisco — Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
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.
9.9
70.7%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- Published
- Sep 25, 2025
- Modified
- Aug 11, 2026
- Added to KEV
- Sep 25, 2025
- Federal patch due
- Sep 26, 2025
CISA required action
The KEV due date refers to the deadline by which FCEB agencies are expected to review and begin implementing the guidance outlined in Emergency Directive (ED) 25-03 (URL listed below in Notes). Agencies must follow the mitigation steps provided by CISA (URL listed below in Notes) and vendor’s instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
Weakness classification
Affected packages
Proof-of-concept & exploitation references
3 foundWeaponization
Public repositories whose name or description references CVE-2025-20333, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit - cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
- cobbbex/cve-2025-20333★ 0
updated Aug 31, 2026
- curtishoughton/Cisco-ASA-CVE-2025-20333-Scanner★ 0
Safe Python scanner for Cisco CVE-2025-20333 (Cisco ASA/FTD WebVPN Buffer Overflow)
updated May 16, 2026
- cobbbex/Cisco-ASA-vulnerability-research★ 0
Cisco ASA vulnerability research CVE-2025-20333/CVE-2025-20362
updated Aug 22, 2026
References
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. 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.
How severe is CVE-2025-20333?
CVE-2025-20333 has a CVSS base score of 9.9 out of 10 (CVSS 3.1).
Is CVE-2025-20333 actively exploited in the wild?
Yes. CVE-2025-20333 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added Sep 25, 2025, meaning CISA has confirmed evidence of active exploitation.
What is the EPSS score for CVE-2025-20333?
70.7% - meaning FIRST.org's EPSS model estimates a 70.7% probability this vulnerability will be exploited in the wild within 30 days (99% percentile among all scored CVEs).
Is there exploit tooling available for CVE-2025-20333?
We found 3 public GitHub repositories referencing CVE-2025-20333, though none matched a known Nuclei template or Metasploit module at last check. Review each one before relying on it - see the proof-of-concept section above.
What type of vulnerability is CVE-2025-20333?
CVE-2025-20333 is classified under CWE-120 (Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')).
Cross-checked against
Impactr finds and proves whether CVE-2025-20333 - or flaws like it - are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.
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