Multiple vulnerabilities affect all versions of ASUS routers
Four vulnerabilities include:
- Heap buffer overflow in multiple HTTP headers
CVE: CVE-2017-15655CVSS v3: 9.6
(Administrator needs to login and visit certain page at the router website)Description:
This vulnerability affects new Asus routers with not up-to-date firmware, as well as some older end-of-life routers (e.g. RT-N65R, RT-N65U)
Multiple buffer overflow vulnerabilities in HTTPd server in Asus asuswrt version <=220.127.116.11.376.X. All have been fixed in version 18.104.22.168.378, but this vulnerability was not previously disclosed. Some end-of-life routers have this version as the newest so are vulnerable at this time. This vulnerability allows for RCE with administrator rights when the administrator visits serveral pages.
For example the “Host:” header is vulnerable and allows to override the SystemCmd variable which then allows for RCE when the administrator visits serveral pages (for example the network tools router tab).
PoC (after running this script, when the administrator visists one of several pages which trigger commands e.g. the network tools tab, the script is being run and outputs the contents of nvram to a css file which can be retrived without authentication)
- Highly predictable session tokens
CVE: CVE-2017-15654CVSS v3: 8.3
(Attacker needs administrator interaction and a way to overcome administrator IP check – see next point)Description: The session token is generated for an authenticated user using stdlib rand function. The token generation code looks as follows:
The code initializes the random number generator each time a token is generated with router epoch time.
An attacker can guess a token knowing more or less the time the administrator has logged in.
- Not sufficient logged user IP validation
CVE: CVE-2017-15653CVSS v3: 8.3
(Attacker needs the session token to execute any action without IP check – see point above)Description: An attacker who knows the session token can walkaround the IP verification mechanism by sending requests with a special useragent.
The following PoC will download current router configuration even if issued from a different than the logged user IP address:
- Password stored in plain text
CVE: CVE-2017-15656Description: Asus routers store password in plain text in NVRAM memory. Executing nvram show, or downloading the backup file and decoding it allows anyone to read the administrator password.Having access to telnet (shell) one can execute:
Logged-in information disclousure
An unauthenticated attacker can retrieve information about a logged-in session (if and who [IP address] is currently logged in). This itself is not a vulnerability but together with the two previous it allows for a easy exploit.