CVE intelligence and bounded remediation

CVE-2018-0300 — Cisco Fxos security vulnerability

High CVSS 9

A vulnerability in the process of uploading new application images to Cisco FXOS on the Cisco Firepower 4100 Series Next-Generation Firewall (NGFW) and Firepower 9300 Security Appliance could allow an authenticated, remote attacker using path traversal techniques to create or overwrite arbitrary files on an affected device. The vulnerability is due to insufficient validation during the application image upload process. An attacker could exploit this vulnerability by creating an application image containing malicious code and installing the image on the affected device using the CLI or web-based user interface (web UI). These actions occur prior to signature verification and could allow the attacker to create and execute arbitrary code with root privileges. Note: A missing or invalid signature in the application image will cause the upload process to fail, but does not prevent the exploit. Cisco Bug IDs: CSCvc21901.

Severity
High
CVSS
9 (2.0)
Published
2018-06-21
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-22

Affected products

  • cisco / fxos / 2.0(1.68)

Showing 1 representative product identities from 2 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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