ProFTPD before 1.3.5e and 1.3.6 before 1.3.6rc5 controls whether the home directory of a user could contain a symbolic link through the AllowChrootSymlinks configuration option, but checks only the last path component when enforcing AllowChrootSymlinks. Attackers with local access could bypass the AllowChrootSymlinks control by replacing a path component (other than the last one) with a symbolic link. The threat model includes an attacker who is not granted full filesystem access by a hosting provider, but can reconfigure the home directory of an FTP user.
Upstream patch (1.3.5 branch):
Created proftpd tracking bugs for this issue:
Affects: epel-all [bug 1439696]
Affects: fedora-all [bug 1439695]
The patch is buggy: See Bugreport #1443507
FIXED and released on 2017-05-12 15:23:46 EDT
Please close this BR.
See bug 1697508, asking if this can be closed.