CVE-2025-20251: cisco cisco adaptive security appliance (asa) software

Vulnerability summary

CVE-2025-20251 is a high (CVSS 8.5) vulnerability in cisco cisco adaptive security appliance (asa) software. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39.2% of scored vulnerabilities.

Timeline

1. 14-08-2025
   PublishedVulnerability first disclosed.
2. 14-08-2025
   Last modifiedVulnerability information updated.

Description

A vulnerability in the Remote Access SSL VPN service for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to create or delete arbitrary files on the underlying operating system. If critical system files are manipulated, new Remote Access SSL VPN sessions could be denied and existing sessions could be dropped, causing a denial of service (DoS) condition. An exploited device requires a manual reboot to recover. This vulnerability is due to insufficient input validation when processing HTTP requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to create or delete files on the underlying operating system, which could cause the Remote Access SSL VPN service to become unresponsive. To exploit this vulnerability, the attacker must be authenticated as a VPN user of the affected device.

• CWE-1287Improper Validation of Specified Type of InputThe product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type.