ProFTPD AllowChrootSymlinks Configuration Option Bypass Vulnerability [CVE-2017-7418]

CVE number – CVE-2017-7418

A vulnerability in ProFTPD could allow a local attacker to bypass security restrictions on a targeted system.

The vulnerability exists because the affected software, when using the AllowChrootSymlinks offconfiguration option, checks only if the last component of the path is a symbolic link (symlink) instead of checking the entire DefaultRoot path for symlinks. An attacker could exploit this vulnerability to bypass the AllowChrootSymlinks control by replacing a path component other than the last component in the path with a symlink. A successful exploit could be used to conduct further attacks. 

ProFTPD has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.

Safeguards

• Administrators are advised to apply the appropriate updates.
  
  Administrators are advised to allow only trusted users to access local systems.
  
  Administrators are advised to allow only privileged users to access administration or management systems.
  
  Administrators are advised to monitor critical systems.

Vendor Announcements

• ProFTPD has released a bug report at the following link: Bug #4295

Fixed Software

• ProFTPD has released software updates and a git commit at the following links: ProFTPD 1.3.5e and 1.3.6 and commit 349addc3be4fcdad9bd4ec01ad1ccd916c898ed8