CVE-2024-20481: Cisco ASA and FTD Denial-of-Service Vulnerability

Vulnerability summary

CVE-2024-20481 is a medium (CVSS 5.8) vulnerability in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD). It is known to be exploited: CISA lists it, first on 24-10-2024. EPSS estimates a 15.87% chance of exploitation in the next 30 days, higher than 96.8% of scored vulnerabilities.

Timeline

1. 23-10-2024
   PublishedVulnerability first disclosed.
2. 24-10-2024
   Added to CISA KEVCisco ASA and FTD Denial-of-Service Vulnerability
3. 14-11-2024
   CISA remediation dueApply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
4. 21-10-2025
   Last modifiedVulnerability information updated.

Description

A vulnerability in the Remote Access VPN (RAVPN) service of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.

• CWE-772Missing Release of Resource after Effective LifetimeThe product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.