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Vulnerabilities

Vulnerability · CVE-2025-20333

Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

Published Sep 25, 2025 · catalog updated Aug 11, 2026 · Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense

Patch now

CVE-2025-20333 is in the CISA known-exploited catalog, due Sep 26, 2025. Confirm Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
Critical9.9
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
71.21%
Remediation
Remediation guidance
Affected products
cpe cisco/adaptive security appliance software · cpe cisco/secure firewall threat defense · vendor Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe cisco/adaptive security appliance softwareversion unspecified
  • cpe cisco/secure firewall threat defenseversion unspecified
  • vendor Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defenseversion unspecified

How to fix CVE-2025-20333

  • Recommended remediation

    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. CISA due date Sep 26, 2025.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2025-20333 is in the CISA known-exploited catalog, due Sep 26, 2025. Confirm Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. 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.

What should an analyst verify?

CWE-120: Classic Buffer Overflow. EPSS 71.21%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 25, 2025 · Catalog

    Detected

    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

  2. Sep 25, 2025 · CISA KEV

    Known exploited

    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 o

  3. Sep 26, 2025 · CISA KEV

    Remediation due

    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 o

  4. Aug 11, 2026 · Catalog

    Updated

    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

Sources

  • CISA KEVConfirmed exploitationCVE-2025-20333

    Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Software VPN Web Server contain a buffer overflow vulnerability that allows for remote code execution. This vulnerability could be chained with CVE-2025-20362.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2025-20333

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-20333

    30-day exploitation probability 71.2%

    first.org
  • NIST NVDVulnerability recordCVE-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 i

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2025-20333

    Cisco Secure Firewall Adaptive Security (ASA) Appliance and Secure Firewall Threat Defense (FTD) Software VPN Web Server contain a buffer overflow vulnerability that allows for remote code execution. This vulnerability could be chained with CVE-2025-20362.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.