CVE-2021-1501: Cisco Adaptive Security Appliance Software

High severity, CVSS 7.5. EPSS: 1.4% chance of exploitation in the next 30 days.

A vulnerability in the SIP inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affected device, resulting in a denial of service (DoS) condition.The vulnerability is due to a crash that occurs during a hash lookup for a SIP pinhole connection. An attacker could exploit this vulnerability by sending crafted SIP traffic through an affected device. A successful exploit could allow the attacker to cause a crash and reload of the affected device.

Affected products

• Cisco Adaptive Security Appliance Software: from 9.8, before 9.8.4.34 (fixed in 9.8.4.34); from 9.9, before 9.9.2.85 (fixed in 9.9.2.85); from 9.10, before 9.12.4.18 (fixed in 9.12.4.18); from 9.13, before 9.13.1.21 (fixed in 9.13.1.21); from 9.14, before 9.14.2.13 (fixed in 9.14.2.13); from 9.15, before 9.15.1.15 (fixed in 9.15.1.15)
• Cisco Secure Firewall Threat Defense: from 6.2.2, before 6.4.0.12 (fixed in 6.4.0.12); from 6.5.0, before 6.6.4 (fixed in 6.6.4); from 6.7.0, before 6.7.0.2 (fixed in 6.7.0.2)

Published 2021-04-29. Last modified 2026-08-11.