CVE-2025-20135: cisco cisco adaptive security appliance (asa) software

Vulnerability summary

CVE-2025-20135 is a medium (CVSS 4.3) vulnerability in cisco cisco adaptive security appliance (asa) software. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 9% of scored vulnerabilities.

Timeline

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

Description

A vulnerability in the DHCP client functionality of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, adjacent attacker to exhaust available memory. This vulnerability is due to improper validation of incoming DHCP packets. An attacker could exploit this vulnerability by repeatedly sending crafted DHCPv4 packets to an affected device. A successful exploit could allow the attacker to exhaust available memory, which would affect availability of services and prevent new processes from starting, resulting in a Denial of Service (DoS) condition that would require a manual reboot. Note: On Cisco Secure FTD Software, this vulnerability does not affect management interfaces.

• CWE-401Missing Release of Memory after Effective LifetimeThe product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.