CVE-2020-3436: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Services File Upload Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-10-21 · updated 2026-08-11
Weakness: CWE-434

Description

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 ASA Software: from 9.8.0 before 9.8.4.25; from 9.9.0 before 9.9.2.80; from 9.10.0 before 9.10.1.44; from 9.12.0 before 9.12.4.2; from 9.13.0 before 9.13.1.12; from 9.14.0 before 9.14.1.15 — fixed in 9.10.1.44, 9.12.4.2, 9.13.1.12, 9.14.1.15, 9.8.4.25, 9.9.2.80
Cisco Firepower Threat Defense Software: through 6.2.2; from 6.3.0 before 6.3.0.6; from 6.4.0 before 6.4.0.10; from 6.5.0 before 6.5.0.5; 6.6.0 — fixed in 6.3.0.6, 6.4.0.10, 6.5.0.5

How to fix

Upgrade to a fixed version: Cisco Adaptive Security Appliance 9.6.4.45; Cisco ASA Software 9.10.1.44, 9.12.4.2, 9.13.1.12, 9.14.1.15; Cisco Firepower Threat Defense Software 6.3.0.6, 6.4.0.10, 6.5.0.5. Check the vendor advisory for mitigations.

References

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