Jenkins 2.333 and earlier, LTS 2.319.2 and earlier defines custom XStream converters that have not been updated to apply the protections for the vulnerability CVE-2021-43859 and allow unconstrained resource usage.
Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:NI:NA:H7.5/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H