In rsync 3.0.1 through 3.4.1, receivexattr 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.

The checksecret function in authenticate.c in rsync 3.1.0 and earlier allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via a user name which does not exist in the secrets file.