http://lists.busybox.net/pipermail/busybox/2013-February/078927.html

--- busybox-1.20.2.org/archival/libarchive/decompress_unxz.c
+++ busybox-1.20.2/archival/libarchive/decompress_unxz.c
@@ -86,8 +86,40 @@
 			IF_DESKTOP(total += iobuf.out_pos;)
 			iobuf.out_pos = 0;
 		}
-		if (r == XZ_STREAM_END) {
-			break;
+		while (r == XZ_STREAM_END) {
+			/* Handle concatenated .xz Streams including possible
+			 * Stream Padding.
+			 */
+			if (iobuf.in_pos == iobuf.in_size) {
+				int rd = safe_read(src_fd, membuf, BUFSIZ);
+				if (rd < 0) {
+					bb_error_msg(bb_msg_read_error);
+					total = -1;
+					goto out;
+				}
+				if (rd == 0)
+					goto out;
+
+				iobuf.in_size = rd;
+				iobuf.in_pos = 0;
+			}
+
+			/* Stream Padding must always be a multiple of four
+			 * bytes to preserve four-byte alignment. To keep the
+			 * code slightly smaller, we aren't as strict here as
+			 * the .xz spec requires. We just skip all zero-bytes
+			 * without checking the alignment and thus can accept
+			 * files that aren't valid, e.g. the XZ Utils test
+			 * files bad-0pad-empty.xz and bad-0catpad-empty.xz.
+			 */
+			while (iobuf.in_pos < iobuf.in_size) {
+				if (membuf[iobuf.in_pos] != 0) {
+					xz_dec_reset(state);
+					r = XZ_OK;
+					break;
+				}
+				++iobuf.in_pos;
+			}
 		}
 		if (r != XZ_OK && r != XZ_UNSUPPORTED_CHECK) {
 			bb_error_msg("corrupted data");
@@ -95,6 +127,8 @@
 			break;
 		}
 	}
+
+out:
 	xz_dec_end(state);
 	free(membuf);