CVE-2020-3436: Cisco Adaptive Security Appliance

High severity, CVSS 8.6. EPSS: 1.9% chance of exploitation in the next 30 days.

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to upload arbitrary-sized files to specific folders on an affected device, which could lead to an unexpected device reload. The vulnerability exists because the affected software does not efficiently handle the writing of large files to specific folders on the local file system. An attacker could exploit this vulnerability by uploading files to those specific folders. A successful exploit could allow the attacker to write a file that triggers a watchdog timeout, which would cause the device to unexpectedly reload, causing a denial of service (DoS) condition.

Affected products

• Cisco Adaptive Security Appliance: before 9.6.4.45 (fixed in 9.6.4.45)
• Cisco Adaptive Security Appliance Software: from 9.8.0, before 9.8.4.25 (fixed in 9.8.4.25); from 9.9.0, before 9.9.2.80 (fixed in 9.9.2.80); from 9.10.0, before 9.10.1.44 (fixed in 9.10.1.44); from 9.12.0, before 9.12.4.2 (fixed in 9.12.4.2); from 9.13.0, before 9.13.1.12 (fixed in 9.13.1.12); from 9.14.0, before 9.14.1.15 (fixed in 9.14.1.15)
• Cisco Secure Firewall Threat Defense: up to and including 6.2.2; from 6.3.0, before 6.3.0.6 (fixed in 6.3.0.6); from 6.4.0, before 6.4.0.10 (fixed in 6.4.0.10); from 6.5.0, before 6.5.0.5 (fixed in 6.5.0.5); version 6.6.0 only

Published 2020-10-21. Last modified 2026-08-11.