Skip to main content

Improper Certificate Validation


Severity Medium
Score 4.7/10


Nextcloud also ships a CLI utility called nextcloudcmd which is sometimes used for automated scripting and headless servers. Versions of nextcloudcmd prior to 3.6.1 would incorrectly trust invalid TLS certificates, which may enable a Man-in-the-middle attack that exposes sensitive data or credentials to a network attacker. This affects the CLI only. It does not affect the standard GUI desktop Nextcloud clients, and it does not affect the Nextcloud server.

  • HIGH
  • HIGH
  • NONE
  • LOW
  • NONE
  • NONE

CWE-295 - Improper Certificate Validation

The authenticity component of a web system stems from the ability to validate “Digital certificates”, which (i) establish trust between two or more entities sharing data over a network; (ii) ensure data at rest and transit is secure from unauthorized access; and (iii) check the identity of the actors that interact with the system. An application with absent or ineffective certificate validation mechanisms allows malicious users, impersonating trusted hosts, to manipulate the communication path between the client and the host, resulting in unauthorized access to data and to the application’s internal environment, and potentially enabling man-in-the-middle attacks.


Advisory Timeline

  • Published