How I saved your a** from the ZynOS (rom-0) attack !! ( Full disclosure )

Hello everyone, I just wanted to discuss some vulnerability I found and exploited for GOODNESS .. just so that SCRIPT KIDIES won’t attack your home/business network .

Well, in Algeria the main ISP ( Algerie Telecom ) provide you with a router when you pay for an internet plan. So you can conclude that every subscriber is using that router . TD-W8951ND is one of them, I did some ip scanning and I found that every router is using ZYXEL embedded firmware.

Analysis :

Let’s download an update and take a look at it and try to find some vulnerabilities. ( )


The ras file is in LIF format !! …
Hmmm let’s put that file for Binwalk test for God’s sake ! ( check : for more informations on how to install it ).

This is what Binwalk told me about that file :

You can clearly see and confirm that the router is using zynos firmware. We can also see that there is two blocks of LZMA compressed data … let’s extract them and have a look.

The problem is that when I tried to decompress the two blocks I get an error : ” Compressed data is corrupt “Image

Hmm, first the “ras” file was in LIF format .. and now the lzma compress blocks are corrupted !!
I googled this and tried to find a solution for this, FOUND NOTHING . How am I going to solve this ??
One idea came in my mind .. “Strings” command and here is what I got :


Aaaah ! so the blocks aren’t compressed with LZMA or anything ! and the whole “ras” firmware file is just big chunk of data in clear text.
Ok, let’s try and find some useful STRINGS …

After some time searching “I” didn’t find the useful thing that will help us find vulnerabilities on the firmware !!

I didn’t give up …
I just was thinking and questioning :

  • Me: What do you want from this firmware file !
  • Me: I want to find remote vulnerabilities that will help me extract the “admin” password.
  • Me: Does the web interface let you save the current configuration ?


  • Me: yes !!
  • Me: Is the page password protected ?


  • Me: No !!! I tired to access that page on a different IP and it didn’t require a passowrd !

Ok, enough questions haha ..

Now, when I activated TamperData and clicked “ROMFILE SAVE”  I’ve found out that the rom-0 file is located on “IP/rom-0” and the directory isn’t password protected or anything.

So we are able to download the configuration file which contains the “admin” password. I took a look at rom-0 file and couldn’t figure out how to reverse-engineer it, and when you don’t know something it’s not a shame to ask for help .. and that’s what I did !
I contacted “Craig” from, he is an expect when it comes to hacking embdded devices . He’s a great guy and he replied to my email and pointed me to which is a free rom-0 file decompressor .


When you upload and submit the rom-0 file there, the php page replies back with the configuration in clear text ( INCLUDING THE PASSWORD ) .

So what i need to do now is to automate the process of :

  • Download rom-0 file.
  • Upload it to
  • get the repy back and extract the admin password from it.
  • loop this process to a range of ip addresses.

And that’s exactly what I did, I opened an OLD OLD poc python script of mine that accessed routers via telnet using the default passwords. So what I just need to do now is to add some functionality to it.

Well I thought about  this, and I’m posting this script online ONLY FOR EDUCATIONAL PURPOSES.

You can find the scripts here :

Demo :



Prevention :

Now ! how do you prevent attackers from downloading your rom-0 configuration file and manipulating your router ? This is pretty simple if you think about it ..
You just have to forward port 80 on the router to and inused IP address on your network :

THATS ALL, or if you want to play a little with attackers that are using scripts too .. just forward port 80 to you local http server and put a LARGE file in the root directory and name it rom-0 .. just let them download like 1GB rom-0 file haha haha .. I have also automated the process of port forwarding and I’m running the scripts daily just to prevent hackers from attacking weak users …

In the next post I’ll demonstrate how would a malicious hacker exploit this to hack TONS of networks and get a meterpreter/reverse_shell on every PC on the target network ..

Hope you enjoyed this analysis, if you have anything to add or any questions to ask don’t hesitate to contact me ! BE THEIR HERO, HAPPY HACKING 😉


The decoded.php script is now located at : , I have updated the script


113 thoughts on “How I saved your a** from the ZynOS (rom-0) attack !! ( Full disclosure )

  1. It is really a great article and well-explained, I will give it a try on this router which i am using right now at ” INELEC ” XD ,, THX , Keep it up (y)

  2. In actual fact, you do not even need to decrypt the password. Just work on a similar model, save your own password into the file and overwrite it by uploading your rom-0. Yes, the upload function is not protected as well. ^_^

    1. Well I tried this , but you’ll then lose the target as it’ll reboot and will be assigned with new IP address .. 🙂

      1. No No 🙂 you can
        1- add new user and password and try to find him again by hydra
        2- dyndns
        3- port forward unique port and scan the network for him

  3. salem, nasro khoya ellah yahafdek wi berk fik mais j’ai pas pu faire la manip qui consiste a changer le serveur virtuel je ne trouve pas la page correspondante sur mon routeur merci de me guider et bonne continuation.

  4. Re-salem, en fin de compte j’ai pu faire la manip j’ai juste aller fouiner un peu du coté de la NAT et puis j’ai accedé au virtual server et j’ai suivi votre exemple merci beaucoup mais j’ai quelques questions: est-ce que ta méthode est comme en dit “bulletproof” ou bien doit-je chercher dés maintenant un bon modem-routeur au lieu de ce tp-link merdique? à propos que me conseil-tu comme marque de routeur avec un bon rapport qualité-prix? merci d’avance.

    1. Thanks for your comment :), well .. the prevention method I posted is guaranteed “Port forwarding” and they’ll not be able to extract your rom-0 config file, but only from outside of the network. So if somebody is already inside your LAN and he browse to “” he will still be able to download it.

      If we’re talking about a business network, the best option is to implement a more secured one like “CISCO” ..

    1. Yahh, thanks for your articles. may be blocked by my ISP.

      I found many links pointing to a website at, which should contain the source code of how to decrypt rom-0 file. Unfortunately, it was down and I can’t even find exists.

      Nasro, please write a script or a tool (C#..) to decode rom-0. You can send it to my email. Thank you, I really appreciate it.

      -Educational purposes only- HAPPY HACKING

  5. Anyone else who cannot access, it seems there is a lack of decoders around and this one is offline. However, looking at the cached version of the page links us to the twitter page for @routerpwn, their most recent tweet is to these scripts
    The scripts include a C file that allows for decompression of LZS files. The script expects a single ip and therefore will need to be modified for a range. A mix of this and Nasros scripts should do it.

  6. The Hacker SADAM213 started His baby script !
    he changed the password of the victim router , he put the password : sadam213xx

  7. Nasro, no offense but this is a really (really) old vulnerability. Just take a look at Adrian Pastor’s report from 2008 (6 years ago).

    I’ve come in contact with these babies a long time ago, living in a place where there are many security cameras.

  8. Does the “Router Pass View” program open rom-0 files? Then you wouldn’t need those zynos site alternatives. Let me know here if that program opens rom-0 files. For example, it does decode TP-LINK DES encrypted .bin (or .cfg) switch/router/AP files.

  9. This looks like generic trendchip firmware (Billion, Tplink, Sitecom, Michelangelo, Edimax, Trust, Airline, Topcom, etc). Could be all vulnerable.

  10. Pingback: Anonymous
  11. Thanks for your effort
    I’d like to ask you how to forward port 80 on the router to and inused IP address as I don’t have this settings on my website

    1. Hi,
      If you want to forward port 80 then you have to login to the router dashboard with the IP address like : using the browser then enter the username and password and if you haven’t changed them yet then they should be both “admin”. from there click on “Advanced Setup”->”NAT”-> select the “Virtual Circuit” you are using, if you don’t know that then navigate to “Status” you should find it there (example: PVC2 ). Now go back to “NAT” select the PVC two options should be available now click on “Virtual Server” fill these information under some “Rule index” :

      Application : anything
      Protocol : ALL
      Start Port Number : 80
      End Port Number : 80
      Local IP Address : unused IP address, for example

      And you’re done ! 🙂

      1. Doesn’t work like that in mine. I did as you advised but if I type – my current IP address/rom-0 – the file is still downloadable. My router is constantly attached. The only thing that slows down attackers is to change the gateway IP (along with the subnet one). But eventually the program they run will get my IP (up until now the only thing it does is to reset the router using the IP and setting a random password). When this happen I have to just download the rom-0 file, unpack it and get the new password.

    1. @Nasro, Why you need to port-forward and you have ACL in Access mangment,
      And I think when you forward port:80 the managment port will be 8080, so forwarding will not fix anything.

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