rsync 2.3.3 before 3.5.0 contains a path traversal vulnerability that allows a malicious sender to escape the module root by exploiting symlinks within the module file tree when using --partial-dir or --backup-dir options. Attackers with write access to place a symlink under the module root, or who can exploit a pre-existing trusted symlink, can direct file writes to locations outside the intended module root, achieving arbitrary file write relative to the module root parent.