Buffer overflow in Cisco Secure Firewall Adaptive Security Appliance (Asa) Software

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…

Vulnerability class: Buffer Overflow

EPSS: 0.298 (96.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

Affected products

Weakness classification (CWE)

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: .

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.

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2025-20333?
CVE-2025-20333 is a critical-severity vulnerability in Cisco Secure Firewall Adaptive Security Appliance (Asa) Software, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.9/10. Published 2025-09-25.
How severe is CVE-2025-20333?
Critical severity. CVSS v3 base score is 9.9 out of 10.
Is CVE-2025-20333 known to be exploited?
Yes. CVE-2025-20333 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-09-25), indicating it is being actively exploited. 8 public proof-of-concept repositories are indexed.