In RESTEasy the insecure File.createTempFile() is used in the DataSourceProvider, FileProvider and Mime4JWorkaround classes which creates temp files with insecure permissions that could be read by a local user.
Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:HI:NA:N5.5/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:NOther