DrayTek VigorACS SI ( <= 1.3.0)

Vigor ACS-SI Edition is a Central Management System for DrayTek
routers and firewalls,
providing System Integrators or system administration personnel a
real-time integrated
monitoring, configuration and management platform.

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2.1. Default http-auth username/password used for <ip>/ACSServer/*

We found that most of the VigorACS SI deployments are using the
default http authentication settings (acs/password). This is not so much
a software vulnerability but more a configuration issue.


2.2 Unauthenticated arbitrary file read/write functionality via
UploadDownloadServlet

The UploadDownloadServlet can be used to (read and) write files to the
server directly. In addition, this functionality is accessible without
having to provide the
http authentication details (2.1).


2.3. Path traversal and Local File Inclusion in the FileServlet

The regular expression that is used to prevent this is not sufficient:
it removes occurences of '../' (without the quotes). By providing input
like '....//', the middle '../' will be removed, while the remainder
equals to '../'. We could now use the FileServlet to access any file on
the server:
<ip>/ACSServer/FileServlet?f=....//....//....//....//....//....//....//etc/passwd


2.4. Arbitrary file upload in <ip>/ACSServer/UploadFileServlet

This servlet suffers from the same path traversal vulnerability as
described in 2.2. You can POST data to this servlet to upload files
into arbitrary
locations:
http://<ip>//ACSServer/UploadFileServlet?prefix=<URLENCODED('a&....//....//....//....//....//server/default/deploy/web.war/shell.jsp&a&a&a&a')>

The UploadFileServlet will append '.cfg' to the given filename, this means files
uploaded via this mechanism aren't directly of use by an attacker. However, when
the payload is a ZIP archive, the vuln. in 2.5 (Local unzip functionality)
can be used to unpack an otherwise benign file into an full-blown
remote web-shell.


2.5. Local unzip functionality

The RPC server provides an unzip functionality (rpcmanager.UnZip) that can be
invoked by using the AMF message broker (accessible via
http://<ip>/ACSServer/messagebroker/amf). This functionality can be used
to unzip any file on the file system like one that has been previously uploaded
using the UploadFileServlet vuln.


2.6. ACS runs as root

The webservice is running as the root user.

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Timetable:

2014-09-26 : Vender released patches (private and unverified) to their customers
2014-07-22 : Vendor states that most of the vulns. are patched
2014-07-08 : Vendor notified customers with large deployments
2014-06-30 : Response of Vendor
2014-06-24 : Notified Vendor

Researchers:
Victor van der Veen (vvdveen@cs.vu.nl)
Erik-Paul Dittmer (epdittmer@digitalmisfits.com)


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