Teltonika RUT9XX Reflected Cross Site Scripting

`# Teltonika RUT9XX Reflected Cross-Site Scripting (XSS) #  
  
Link: https://github.com/sbaresearch/advisories/tree/public/2018/SBA-ADV-20180410-01_Teltonika_Cross_Site_Scripting  
  
## Vulnerability Overview ##  
  
Teltonika RUT9XX routers with firmware before 00.05.01.1 are prone to  
cross-site scripting vulnerabilities in `hotspotlogin.cgi` due to  
insufficient user input sanitization.  
  
* **Identifier** : SBA-ADV-20180410-01  
* **Type of Vulnerability** : Cross Site Scripting  
* **Software/Product Name** : [Teltonika RUT955](https://teltonika.lt/product/rut955/)  
* **Vendor** : [Teltonika](https://teltonika.lt/)  
* **Affected Versions** : Firmware RUT9XX_R_00.05.00.5 and probably prior  
* **Fixed in Version** : RUT9XX_R_00.05.01.1  
* **CVE ID** : CVE-2018-17533  
* **CVSSv3 Vector** : CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N  
* **CVSSv3 Base Score** : 8.2 (High)  
  
## Vendor Description ##  
  
> RUT955 is a highly reliable and secure LTE router with I/O, GNSS and  
> RS232/RS485 for professional applications. Router delivers high  
> performance, mission-critical cellular communication and GPS location  
> capabilities.  
  
Source: <https://teltonika.lt/product/rut955/>  
  
## Impact ##  
  
By exploiting the documented vulnerabilities, an attacker can execute  
JavaScript code in a user's browser within the origin of the router.  
The attacker might take over existing or future administrative web  
management sessions and gain access to the device.  
  
We recommend upgrading to version RUT9XX_R_00.05.01.1 or newer, which  
includes fixes for the vulnerabilities described in this advisory.  
  
## Vulnerability Description ##  
  
Several parameters of the script `hotspotlogin.cgi` are affected by  
reflected cross-site scripting vulnerabilities. The scripts are part of  
the coova-chilli captive portal. However, in firmware versions before  
RUT9XX_R_00.04.233 the vulnerabilities are exploitable regardless of  
the device configuration, even if no captive portal is configured.  
  
More concretely, the following parameters are vulnerable:  
  
* `/cgi-bin/hotspotlogin.cgi`  
* *If* res=failed or res=notyet  
* challenge  
* uamip  
* uamport  
* userurl  
  
The affected script outputs these input parameters in an HTML context  
without proper output encoding.  
  
The vulnerabilities are located in `hotspotlogin.cgi`:  
  
```lua  
[...]  
elseif result == 2 or result == 5 then  
replace_tags.formHeader = [[<form name="myForm" method="post" action="]] .. loginpath .. [[">  
<INPUT TYPE="hidden" NAME="challenge" VALUE="]] .. challenge .. [[">  
<INPUT TYPE="hidden" NAME="]] .. names["uamip"] .. [[" VALUE="]] .. uamip .. [[">  
<INPUT TYPE="hidden" NAME="]] .. names["uamport"] .. [[" VALUE="]] .. uamport .. [[">  
<INPUT TYPE="hidden" NAME="]] .. names["userurl"] .. [[" VALUE="]] ..userurldecode .. [[">  
<INPUT TYPE="hidden" NAME="res" VALUE="]] .. res .. [[">]]  
replace_tags.formFooter = [[</form>]]  
[...]  
```  
  
As the above code snippet shows, the parameter `userurl` contains user  
input and is output without performing any HTML escaping.  
  
## Proof-of-Concept ##  
  
An attacker can exploit this vulnerability by manipulating the `userurl`  
query parameter:  
  
```text  
http://<IP>/cgi-bin/hotspotlogin.cgi?res=failed&userurl="><script>alert(1)</script><span  
```  
  
An attacker can exploit the other parameters (e.g. challenge) via POST  
requests:  
  
```html  
<form action="http://<IP>/cgi-bin/hotspotlogin.cgi" method="post" enctype="text/plain">  
<input type="hidden" name="res" value="failed&challenge="><script>alert(1)</script><span"">  
<input type="submit" value="challenge">  
</form>  
```  
  
## Timeline ##  
  
* `2018-04-10` identification of vulnerability in version RUT9XX_R_00.04.161  
* `2018-04-16` re-test of version RUT9XX_R_00.04.172  
* `2018-04-16` initial vendor contact through public address  
* `2018-04-18` vendor response with security contact  
* `2018-04-19` disclosed vulnerability to vendor security contact  
* `2018-04-26` vendor released fix in version RUT9XX_R_00.04.233  
* `2018-07-09` notify vendor about incomplete fix in version RUT9XX_R_00.05.00.5  
* `2018-07-19` vendor released fix in version RUT9XX_R_00.05.01.1  
* `2018-07-25` re-test of version RUT9XX_R_00.05.01.2  
* `2018-09-25` request CVE from MITRE  
* `2018-09-26` MITRE assigned CVE-2018-17533  
* `2018-10-11` public disclosure  
  
## References ##  
  
* Firmware Changelog: <https://wiki.teltonika.lt/index.php?title=RUT9xx_Firmware>  
  
## Credits ##  
  
* David Gnedt ([SBA Research](https://www.sba-research.org/))  
  
`