The poplib module, when passed a user-controlled command, can have additional commands injected using newlines. Mitigation rejects commands containing control characters.
Exploitability
AV:NAC:LAT:PPR:HUI:NVulnerable System
VC:LVI:HVA:NSubsequent System
SC:NSI:NSA:N5.9/CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:NInput Validation