CVE intelligence and bounded remediation

CVE-2020-3436 — Cisco Adaptive Security Appliance security vulnerability

High CVSS 8.6

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.

Severity
High
CVSS
8.6 (3.1)
Published
2020-10-21
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-434

Affected products

  • cisco / adaptive_security_appliance
  • cisco / firepower_threat_defense
  • cisco / firepower_threat_defense / 6.6.0
  • cisco / adaptive_security_appliance_software

Showing 4 representative product identities from 12 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Path traversal, unsafe upload, and file handling

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Check exposure

  • Trace untrusted filenames, archive entries, URLs, and path segments into read, write, include, extraction, and upload operations.
  • Identify filesystem roots, mount permissions, symbolic-link behavior, archive handling, and whether uploaded content is web-accessible or executable.
  • Review canonicalization and containment checks across supported operating systems and storage backends.

Remediate safely

  • Generate server-side storage identifiers and resolve paths beneath a fixed root using filesystem-aware containment checks.
  • Reject absolute, parent-relative, alternate-separator, device, link, and archive entries that escape the intended root.
  • Store uploads outside executable or served paths, validate type and size, and use private atomic temporary files.

Authoritative sources

Complete CVE record and remediation plan

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