Thursday, 26 March 2020

Stealing videos from vlc

VLC for iOS was vulnerable to an unauthenticated insecure direct object reference (IDOR) which could allow a local attacker to steal media from the storage by just navigating to the source URL/IP.

This was possible by abusing a functionality in the iOS application for VLC, which allows a user to share files with others over WiFi. This can be simply done by enabling "Network > Sharing via WiFi" and the web-server for this functionality works on port 80(http) protocol.

Technical analysis:
Let's assume a scenario where Bob & Alice are sharing a video over the WiFi using vlc-iOS, Eve could perform this attack by crawling the source IP address of Bob which would list the URL's of the videos shared between Bob & Alice.

Having said that, navigating to those URL's Eve could simply steal the video without Bob's knowledge which successfully leads to unauthenticated IDOR. 

In the below image, Bob's IP is and the hierarchy of stored videos in Bob's phone would look like,

Such things can be crawled via burpsuite or you can use python scrapy to extract the URL's from the host and download the videos.

Mitigation from VLC Security team:
They implemented a user-friendly authentication mechanism on VLC iOS web server for WiFi Sharing. Passcode authentication is enabled when VLC's passcode setting is enabled and the user uses the passcode that he set in VLC's settings to log into Wifi Sharing.

This was reported on 2nd Jan 2019 and patched on 10th Feb 2020 whereas fixed version was publicly released in March 2020. Post mitigation VLC published an advisory for this which you can view here. Aside this issue was accepted for bounty on The Internet.

Update Friday, 22 May 2020: Advisory from VLC Security[1]

Wednesday, 4 March 2020

Fuzzing VIM

AAAAAAAAAA....: It's almost a year now I started with fuzzing and discovered multiple bugs. The most commonly software which I've fuzzed so far includes Xpdf, VIM, PuTTY, WebKit, LibreOffice, Glibc etc. In this post I'll be demonstrating fuzzing VIM (Regex engine) through AFL++ a.k.a american fuzzy lop.

Technical Details: VIM a.k.a Vi IMproved has 12 different editing modes which can be utilized for fuzzing. Vim has lots of potential for finding bugs with AFL. One of the bug which I found while fuzzing VIM was CVE-2019-20079, I would also like to thank Dominique Pelle for this.
[+] Git clone VIM
cmd$ git clone ; cd vim

[+] Compile and Make VIM with AFL++ 
cmd$ CC=afl-clang-fast CXX=afl-clang-fast++ ./configure --with-features=huge --enable-gui=none
cmd$ make -j4 ; cd src/

[+] Feed Corpus
cmd$ mkdir corpus ; mkdir output 
cmd$ echo "a*b\+\|[0-9]\|\d{1,9}" > corpus/1 ; echo "^\d{1,10}$" > corpus/2

[+] Fuzzing VIM
cmd$ afl-fuzz -m none -i corpus -o output ./vim -u NONE -X -Z -e -s -S @@ -c ':qa!'
The above options used -u NONE and -X is to speed up vim startup. Options -e -s are used to make vim silent and to avoid 'MORE' prompt which could block VIM, the option -Z disables the external commands which makes fuzzing safer. I've also created a small bash script which automates the above tasks for you [].

While fuzzing, fuzz it on ram file system to avoid making too much I/O something like:  sudo mount -t tmpfs -o size=6g tmpfs /home/afl-fuzz-user/afl-fuzz. Aside you can use [] a script which contains some standard ubuntu packages so you dont get much dependence issues while compiling any target. Keep fuzzing :)

Monday, 17 February 2020

Sharepoint RCE

Few days ago I saw a post from alienvault which says attackers are still exploiting SharePoint vulnerability to attack middle east government organization. Having said that I found Income Tax Department India and MIT Sloan was also vulnerable to CVE-2019-0604 a remote code execution vulnerability which exists in Microsoft SharePoint. A malicious actor could exploit this vulnerability by simply sending a specially crafted SharePoint application package.

Technical analysis:
I found this vulnerability during my free time while I was browsing to ZoomEye to find such component. The application ( was found to be vulnerable as it was using SharePoint as a technology to host its service. To verify this I've sent a crafted payload which enable the remote server ( to perform a DNS lookup on my burp collaborator. You can do this manual by sending the crafted XML payload or via desharialize.

Aside, MIT Sloan School of Management was also found to be vulnerable with CVE-2019-0604.

Responsible Disclosure:
CERT-In (IncomeTaxIndia):
This was sent to CERT-In on Feb 12, 2020, got initial response by them on Feb 13, 2020. Post that the vulnerability was patch silently.
For MIT:
This was sent to MIT security team on Feb 13, 2020, got initial response by them on Feb 14, 2020. Post that the vulnerability was patch silently on Feb 15, 2020.

Friday, 13 December 2019

IDOR in Power Service

One of the India's leading power supply company named, Adani Power Limited  is the power business subsidiary of Indian conglomerate Adani Group. A subdomain was vulnerable to IDOR (Insecure Direct Object Reference) which could allow attackers to view bills of any users across India. The bill include details such as Name, Address, Bill Amount, Unit rate, Pervious bill details etc.

I found this vulnerability while using one of their service.

Vulnerable URL:

The parameter `TXTCANO` in the above URL contains 9 random digits which can be predicted, having said that, changing the value of that parameter can allow attackers to view bills of any other users. (Proof Of Concept)!

Chaining bugs - (Viewing Bills to Account Takeover)

If the users are not registered under Adani MyAccount. The bill obtained using the above method contains two important details
i.e. Account number and Meter Number using which an attacker could register users account to perform any fraudulent activity.

It was also observed that when you navigate to the registration page and provide the valid "Account Number" and "Meter Number" the MSISDN associate to that account is also disclosed. (Proof Of Concept)!

PS: The registration process sends an OTP to the mapped MSISDN but it was also identified that there is no rate limiting hence performing a brute-force attack would help attackers to find actual OTP or attackers could simply edit MSISDN and insert their own to get OTP.

Hence attacker now have personally identifiable information (PII) of end user i.e. Name, Address, Phone Number and other details in bill. Such information can aid attackers in conducting targeted attacks such as vishing, information gathering via SMS, attempting to steal payment information by impersonating the actual service provider via SMS or telephonic calls.

As per their about page there are 2.9 million users of Adani Electricity.

Timelines: The vulnerability was responsibly reported to Adani Electricity via group[.]csoc[at]adani[.]com on 9th Nov 2019 and was patched without any acknowledgement on 11th December 2019.


Thursday, 31 October 2019

Hacktivity Badge

So, this year I presented my workshop on fuzzing in Hacktivity which is a two day conference in Budapest, Hungary & I had an amazing experience over there, I would personally endorse infosec geeks to be part of that conference.

Nevertheless, I came across the electronic badge which was provided to every attendee in that conference and here is the introductory part of how to get started with the badge.

The badge runs with the MicroPython on ESP32 (low-power microcontroller) so you can develop apps via MicroPython and once the application is ready, you can upload it to the Hatchery as an egg, and the badge will be able to download and run it.

Connect your badge via USB and run `lsusb` or something alternative of `lsusb` in this case I have used `usb-devices` which prints usb device details.

Further I used `dmseg` to list more details of the connected USB devices.

So this gives a name of the badge which would be helpfully to connect and interact further with the badge using screen.
$ screen /dev/ttyACM0 
Once you are connected a welcome message is shown,

After `Enter` is touch the badge would give you main menu and setting options the badge screen is small so moving forward we would be setting up the WiFi manually via cmdline.

Navigate to Settings --> WiFi and scan for networks, select your SSID and punch in the password.

Now, every time you start your badge or perform any activity which requires WiFi it will auto select the SSID which you configured above and that's how you download/install apps or upgrade the badge firmware.

With the help of MicroPython wiki page I understood different functions for MicroPython and wrote a simple program that displays your name on badge.
Register to Hatchery, then login and upload the above code to Hatchery under a category. In this case I uploaded this code under graphic category with the name  `input`. The below video PoC demonstrates that under Installer section you would have different category, select any one category which fetches the egg's from Hatchery select any one of the egg and the badge will install it.

Once install you can view the output under the badge screen, in this case the name was displayed you can view the badge here.
I've also managed to download the badge firmware which can be found here.