diff -r 034e1e076c77 Lib/ftplib.py
--- a/Lib/ftplib.py	Sun Jan 20 12:18:34 2013 +0200
+++ b/Lib/ftplib.py	Tue Feb 05 21:28:30 2013 +0100
@@ -59,6 +59,11 @@
 class error_proto(Error): pass          # response does not begin with [1-5]
 
 
+class LineTooLong(Error):
+    def __init__(self):
+        Error.__init__(self, "got more than %d bytes" % _MAXLINE)
+
+
 # All exceptions (hopefully) that may be raised here and that aren't
 # (always) programming errors on our side
 all_errors = (Error, OSError, EOFError)
@@ -67,6 +72,7 @@
 # Line terminators (we always output CRLF, but accept any of CRLF, CR, LF)
 CRLF = '\r\n'
 B_CRLF = b'\r\n'
+_MAXLINE = 65536
 
 # The class itself
 class FTP:
@@ -194,7 +200,9 @@
     # Internal: return one line from the server, stripping CRLF.
     # Raise EOFError if the connection is closed
     def getline(self):
-        line = self.file.readline()
+        line = self.file.readline(_MAXLINE + 1)
+        if len(line) > _MAXLINE:
+            raise LineTooLong()
         if self.debugging > 1:
             print('*get*', self.sanitize(line))
         if not line: raise EOFError
@@ -446,7 +454,9 @@
         with self.transfercmd(cmd) as conn, \
                  conn.makefile('r', encoding=self.encoding) as fp:
             while 1:
-                line = fp.readline()
+                line = fp.readline(_MAXLINE + 1)
+                if len(line) > _MAXLINE:
+                    raise LineTooLong()
                 if self.debugging > 2: print('*retr*', repr(line))
                 if not line:
                     break
@@ -496,7 +506,9 @@
         self.voidcmd('TYPE A')
         with self.transfercmd(cmd) as conn:
             while 1:
-                buf = fp.readline()
+                buf = fp.readline(_MAXLINE + 1)
+                if len(buf) > _MAXLINE:
+                    raise LineTooLong()
                 if not buf: break
                 if buf[-2:] != B_CRLF:
                     if buf[-1] in B_CRLF: buf = buf[:-1]
@@ -773,7 +785,9 @@
             fp = conn.makefile('r', encoding=self.encoding)
             with fp, conn:
                 while 1:
-                    line = fp.readline()
+                    line = fp.readline(_MAXLINE + 1)
+                    if len(line) > _MAXLINE:
+                        raise LineTooLong()
                     if self.debugging > 2: print('*retr*', repr(line))
                     if not line:
                         break
diff -r 034e1e076c77 Lib/test/test_ftplib.py
--- a/Lib/test/test_ftplib.py	Sun Jan 20 12:18:34 2013 +0200
+++ b/Lib/test/test_ftplib.py	Tue Feb 05 21:28:30 2013 +0100
@@ -224,6 +224,16 @@
         self.dtp.close_when_done()
         self.rest = None
 
+    def cmd_retrlarge(self, arg):
+        self.push('125 retr ok')
+        if self.rest is not None:
+            offset = int(self.rest)
+        else:
+            offset = 0
+        self.dtp.push("k" * 65537)
+        self.dtp.close_when_done()
+        self.rest = None
+
     def cmd_list(self, arg):
         self.push('125 list ok')
         self.dtp.push(LIST_DATA)
@@ -560,6 +570,9 @@
         received = []
         self.client.retrlines('retr', received.append)
         self.check_data(''.join(received), RETR_DATA.replace('\r\n', ''))
+        self.assertRaises(ftplib.LineTooLong,
+            self.client.retrlines,
+            ('retrlarge'))
 
     def test_storbinary(self):
         f = io.BytesIO(RETR_DATA.encode('ascii'))
diff -r 034e1e076c77 Misc/ACKS
--- a/Misc/ACKS	Sun Jan 20 12:18:34 2013 +0200
+++ b/Misc/ACKS	Tue Feb 05 21:28:30 2013 +0100
@@ -564,6 +564,7 @@
 Jack Jansen
 Bill Janssen
 Thomas Jarosch
+Michał Jastrzębski
 Juhana Jauhiainen
 Zbigniew Jędrzejewski-Szmek
 Julien Jehannet