An issue was discovered in rsync before 3.2.5 that allows malicious remote servers to write arbitrary files inside the directories of connecting peers. The server chooses which files/directories are sent to the client. However, the rsync client performs insufficient validation of file names. A malicious rsync server (or Man-in-The-Middle attacker) can overwrite arbitrary files in the rsync client target directory and subdirectories (for example, overwrite the .ssh/authorized_keys file).

The parse_arguments function in options.c in rsyncd in rsync before 3.1.3 does not prevent multiple --protect-args uses, which allows remote attackers to bypass an argument-sanitization protection mechanism.

The daemon in rsync 3.1.2, and 3.1.3-development before 2017-12-03, does not check for fnamecmp filenames in the daemon_filter_list data structure (in the recv_files function in receiver.c) and also does not apply the sanitize_paths protection mechanism to pathnames found in "xname follows" strings (in the read_ndx_and_attrs function in rsync.c), which allows remote attackers to bypass intended access restrictions.

The receive_xattr function in xattrs.c in rsync 3.1.2 and 3.1.3-development does not check for a trailing '\0' character in an xattr name, which allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) or possibly have unspecified other impact by sending crafted data to the daemon.

rsync 3.1.3-development before 2017-10-24 mishandles archaic checksums, which makes it easier for remote attackers to bypass intended access restrictions. NOTE: the rsync development branch has significant use beyond the rsync developers, e.g., the code has been copied for use in various GitHub projects.

The check_secret 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.

rsync 3.x before 3.0.8, when certain recursion, deletion, and ownership options are used, allows remote rsync servers to cause a denial of service (heap memory corruption and application crash) or possibly execute arbitrary code via malformed data.

Buffer overflow in rsync 2.6.9 to 3.0.1, with extended attribute (xattr) support enabled, might allow remote attackers to execute arbitrary code via unknown vectors.