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.
Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:NI:HA:N5.5/CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N