diff --git a/borg/archive.py b/borg/archive.py
index 4d436c860..df1caa6ff 100644
--- a/borg/archive.py
+++ b/borg/archive.py
@@ -23,7 +23,7 @@ from .helpers import Error, uid2user, user2uid, gid2group, group2gid, bin_to_hex
 from .platform import acl_get, acl_set
 from .chunker import Chunker
 from .hashindex import ChunkIndex
-from .repository import Repository
+from .repository import Repository, LIST_SCAN_LIMIT
 
 import msgpack
 
@@ -882,7 +882,7 @@ class ArchiveChecker:
         self.chunks = ChunkIndex(capacity)
         marker = None
         while True:
-            result = self.repository.list(limit=10000, marker=marker)
+            result = self.repository.list(limit=LIST_SCAN_LIMIT, marker=marker)
             if not result:
                 break
             marker = result[-1]
diff --git a/borg/archiver.py b/borg/archiver.py
index 337c03fd6..420cfb32f 100644
--- a/borg/archiver.py
+++ b/borg/archiver.py
@@ -29,7 +29,7 @@ from .logger import create_logger, setup_logging
 logger = create_logger()
 from .compress import Compressor
 from .upgrader import AtticRepositoryUpgrader, BorgRepositoryUpgrader
-from .repository import Repository
+from .repository import Repository, LIST_SCAN_LIMIT
 from .cache import Cache
 from .key import key_creator, tam_required_file, tam_required, RepoKey, PassphraseKey
 from .keymanager import KeyManager
@@ -813,7 +813,7 @@ class Archiver:
         marker = None
         i = 0
         while True:
-            result = repository.list(limit=10000, marker=marker)
+            result = repository.list(limit=LIST_SCAN_LIMIT, marker=marker)
             if not result:
                 break
             marker = result[-1]
diff --git a/borg/remote.py b/borg/remote.py
index 30291cba3..f0dbc9cf5 100644
--- a/borg/remote.py
+++ b/borg/remote.py
@@ -15,7 +15,7 @@ from . import __version__
 from .helpers import Error, IntegrityError, sysinfo
 from .helpers import replace_placeholders
 from .helpers import bin_to_hex
-from .repository import Repository
+from .repository import Repository, LIST_SCAN_LIMIT, MAX_OBJECT_SIZE
 from .logger import create_logger
 
 import msgpack
@@ -46,6 +46,27 @@ def os_write(fd, data):
     return amount
 
 
+def get_limited_unpacker(kind):
+    """return a limited Unpacker because we should not trust msgpack data received from remote"""
+    args = dict(use_list=False,  # return tuples, not lists
+                max_bin_len=0,  # not used
+                max_ext_len=0,  # not used
+                max_buffer_size=3 * max(BUFSIZE, MAX_OBJECT_SIZE),
+                max_str_len=MAX_OBJECT_SIZE,  # a chunk or other repo object
+                )
+    if kind == 'server':
+        args.update(dict(max_array_len=100,  # misc. cmd tuples
+                         max_map_len=100,  # misc. cmd dicts
+                         ))
+    elif kind == 'client':
+        args.update(dict(max_array_len=LIST_SCAN_LIMIT,  # result list from repo.list() / .scan()
+                         max_map_len=100,  # misc. result dicts
+                         ))
+    else:
+        raise ValueError('kind must be "server" or "client"')
+    return msgpack.Unpacker(**args)
+
+
 class ConnectionClosed(Error):
     """Connection closed by remote host"""
 
@@ -115,7 +136,7 @@ class RepositoryServer:  # pragma: no cover
         # Make stderr blocking
         fl = fcntl.fcntl(stderr_fd, fcntl.F_GETFL)
         fcntl.fcntl(stderr_fd, fcntl.F_SETFL, fl & ~os.O_NONBLOCK)
-        unpacker = msgpack.Unpacker(use_list=False)
+        unpacker = get_limited_unpacker('server')
         while True:
             r, w, es = select.select([stdin_fd], [], [], 10)
             if r:
@@ -205,7 +226,7 @@ class RemoteRepository:
         self.cache = {}
         self.ignore_responses = set()
         self.responses = {}
-        self.unpacker = msgpack.Unpacker(use_list=False)
+        self.unpacker = get_limited_unpacker('client')
         self.p = None
         testing = location.host == '__testsuite__'
         borg_cmd = self.borg_cmd(args, testing)
diff --git a/borg/repository.py b/borg/repository.py
index e85c33d6f..71954d32c 100644
--- a/borg/repository.py
+++ b/borg/repository.py
@@ -26,6 +26,8 @@ TAG_PUT = 0
 TAG_DELETE = 1
 TAG_COMMIT = 2
 
+LIST_SCAN_LIMIT = 10000  # repo.list() / .scan() result count limit the borg client uses
+
 
 class Repository:
     """Filesystem based transactional key value store