Actively exploited in the wild

Cisco ASA and FTD Denial-of-Service Vulnerability

Cisco - Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) · Listed in the CISA KEV since 2024-10-24. This indicates confirmed attacks in production environments.

Required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

CVE-2024-20481

MediumCVSS 5.8KEV

Published: 23/10/2024(UTC)Updated: 11/08/2026(UTC)Translated: 12/08/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Very high risk

15.85%

97th percentile - higher than 97% of all known CVEs

Summary

A vulnerability in the Remote Access VPN (RAVPN) service of Cisco ASA and FTD Software allows an unauthenticated, remote attacker to cause a denial of service (DoS) of the RAVPN service. The issue is due to resource exhaustion. A successful exploit could exhaust resources, resulting in DoS of the RAVPN service, and a device reload may be required to restore service.

Risk Assessment

Risk of VPN service disruption, impacting remote access availability, but non-VPN services remain unaffected.

Recommendation

Apply Cisco updates and monitor the number of VPN authentication requests to detect brute-force attacks.

Original NVD description (English source)

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.