The Linux kernel before 5.4.1 on powerpc allows Information Exposure because the Spectre-RSB mitigation is not in place for all applicable CPUs, aka CID-39e72bf96f58. This is related to arch/powerpc/kernel/entry_64.S and arch/powerpc/kernel/security.c.
Exploitability
AV:LAC:HPR:LUI:NScope
S:UImpact
C:HI:NA:N4.7/CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N