In rsync 3.0.1 through 3.4.1, receive_xattr relies on an untrusted length value during a qsort call, leading to a receiver use-after-free. The victim must run rsync with -X (aka --xattrs). On Linux, many (but not all) common configurations are vulnerable. Non-Linux platforms are more widely vulnerable.
Exploitability
AV:NAC:LPR:LUI:NScope
S:CImpact
C:LI:LA:L7.4/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:LOther