CVEs / CVE-2024-20353

CVE-2024-20353: Cisco ASA and FTD Denial of Service Vulnerability

• Known exploited in the CISA KEV catalog since 24 Apr 2024
• high 8.6 CVSS 3.1 (NVD)
• EPSS 69.8% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
• Last changed at its sources 11 Aug 2026

Summary

Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an infinite loop vulnerability that can lead to remote denial of service condition.

Description

A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.

Affected and fixed versions

Exploitation

Severity

References

• CVE-2024-20353 on NVD
• CVE-2024-20353 in the CISA KEV catalog
• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2 (cited by CISA)
• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-websrvs-dos-X8gNucD2 Vendor Advisory
• https://blog.talosintelligence.com/arcanedoor-new-espionage-focused-campaign-found-targeting-perimeter-network-devices/ Exploit, Third Party Advisory
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-20353 US Government Resource