Citrix NetScaler VPX through NS12.0 53.13.nc allows an SSRF attack via the /rapi/read_url URI by an authenticated attacker who has a webapp account. The attacker can gain access to the nsroot account, and execute remote commands with root privileges.
https://support.citrix.com/article/CTX232161
https://gist.github.com/buxu/04ce809eb8b32ef57e232eab5e61f023