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CVE-2025-20333: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow Vulnerability

CVE-2025-20333 is rated critical with a CVSS v3.1 base score of 9.9 and affects Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense, along with 1 other product in NVD’s configuration data. Per its scoring, it can be exploited over the network, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available. CISA added it to its Known Exploited Vulnerabilities catalog on 2025-09-25, which means exploitation in the wild has been observed.

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.

Severity breakdown

CVSS v3.1 9.9: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

  • Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Privileges required: Low. A basic user account is enough.
  • User interaction: None. No action from any user is needed.
  • Scope: Changed. Impact reaches beyond the vulnerable component to other resources.
  • Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
  • Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
  • Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-120: Buffer Copy without Checking Size of Input

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

Affected products

  • Cisco Secure Firewall Threat Defense: from 7.0.0 before 7.0.8.1; from 7.1.0 before 7.2.9; from 7.3.0 before 7.4.2.4; 7.6.0
  • Cisco Adaptive Security Appliance Software: from 9.12 before 9.12.4.72; from 9.14 before 9.14.4.28; from 9.16 before 9.16.4.85; from 9.17.0 before 9.17.1.45; from 9.18 before 9.18.4.47; from 9.19 before 9.19.1.37; from 9.20 before 9.20.3.7; from 9.22 before 9.22.1.3

References