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CVE-2018-19945: QNAP Qts: Improper Input Validation

CVE-2018-19945 is rated critical with a CVSS v3.1 base score of 9.1 and affects QNAP Qts. Per its scoring, it can be exploited over the network, without authentication, without any user interaction.

Vulnerability description

A vulnerability has been reported to affect earlier QNAP devices running QTS 4.3.4 to 4.3.6. Caused by improper limitations of a pathname to a restricted directory, this vulnerability allows for renaming arbitrary files on the target system, if exploited. QNAP have already fixed this vulnerability in the following versions: QTS 4.3.6.0895 build 20190328 (and later) QTS 4.3.4.0899 build 20190322 (and later) This issue does not affect QTS 4.4.x or QTS 4.5.x.

Severity breakdown

CVSS v3.1 9.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

  • Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: None. No action from any user is needed.
  • Scope: Unchanged. Impact stays within the vulnerable component.
  • Confidentiality impact: None. No loss of confidentiality.
  • Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
  • Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-20: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

CWE-22: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

CWE-73: External Control of File Name or Path

The product allows user input to control or influence paths or file names that are used in filesystem operations.

Affected products

  • QNAP Qts: from 4.3.4 before 4.3.4.0899; from 4.3.5 before 4.3.6.0895

References