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Login bypass when using the external FTP user backend

Platform: ownCloud Server

Versions: 5.0.18, 6.0.6,

Date: 11/25/2014

Risk level: High

Description

ownCloud provides multiple user backends that can be used to authenticate users.

One of those backend providers is “user_external”, which authenticates users against FTP, IMAP or SMB servers. This is mainly useful when it is not possible to authenticate against an LDAP server.

The FTP backend provided by “user_external” was not properly URL-encoding the password. Thus, an attacker may use a specially crafted password to login to the remote server.

If the ownCloud instance is able to access external FTP servers this effectively allows an adversary to login without providing valid credentials, if the “user_external” FTP backend has been enabled and configured.

Affected Software

  • ownCloud Server < 6.0.6 (CVE-2014-9045)
  • ownCloud Server < 5.0.18 (CVE-2014-9045)

Action Taken

The FTP user backend within “user_external” is now properly encoding the credentials.

Acknowledgements

The ownCloud team thanks the following people for their research and responsible disclosure of the above advisory:

  • Lukas Reschke – ownCloud Inc. (lukas@owncloud.com) – Vulnerability discovery and disclosure.

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