Skip to content
Switch branches/tags

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time


Eclipser is a binary-based fuzz testing tool that improves upon classic coverage-based fuzzing by leveraging a novel technique called grey-box concolic testing. The details of the technique can be found in our paper "Grey-box Concolic Testing on Binary Code", which is published in ICSE 2019.


Eclipser currently supports Linux ELF binaries, and has been tested on Debian and Ubuntu. Eclipser is written in F# and runs on .NET Core. Also, Eclipser performs program instrumentation based on QEMU code.

  1. Install dependencies
$ sudo vim /etc/apt/sources.list # Uncomment the lines starting with 'deb-src'.
$ sudo apt-get update
$ sudo apt-get build-dep qemu
$ sudo apt-get install libtool libtool-bin wget automake autoconf bison gdb python
  1. Install .NET Core

Installation differs for each Linux distribution, so please refer to this link. Choose your Linux distribution and version from the tab and follow the instructions.

  1. Clone and build Eclipser
$ git clone
$ cd Eclipser
$ make


  • Running with AFL

Starting from v2.0, Eclipser only performs grey-box concolic testing for test case generation and relies on AFL to perform random-based fuzzing (for the context of this decision, refer to Eclipser v2.0 section below). Therefore, you should first launch AFL instances in parallel mode. Although it is possible to run Eclipser alone, it is intended only for simple testing and not for realistic fuzzing.

$ AFL_DIR/afl-fuzz -i <seed dir> -o <sync dir> -M <ID 1> \
  -f <input file to fuzz> -Q -- <target program cmdline>
$ AFL_DIR/afl-fuzz -i <seed dir> -o <sync dir> -S <ID 2> \
  -f <input file to fuzz>  -Q -- <target program cmdline>
$ dotnet ECLIPSER_DIR/build/Eclipser.dll \
  -t <timeout (sec)> -i <seed dir (optional)> -s <sync dir> -o <output dir> \
  -p <target program> --arg <target program cmdline> -f <input file to fuzz>

We note that the output directory for Eclipser should be placed under the synchronization directory (e.g. -s ../syncdir -o ../syncdir/eclipser-output). AFL will automatically create an output directory under the synchronization directory, using its specified ID. This way, Eclipser and AFL will share test cases with each other. To obtain the final result of the fuzzing, retrieve all the test cases under <sync dir>/*/queue/ and <sync dir>/*/crashes/.

Similarly to AFL, Eclipser will fuzz the file input specified by -f option, and fuzz the standard input when -f option is not provided. However, Eclipser does not support @@ syntax used by AFL.

  • Examples

You can find simple example programs and their fuzzing scripts in examples directory. An example script to run Eclipser with AFL can be found here. Note that we create separate working directories for each AFL instance and Eclipser in this script. This is to prevent the instances from using the same input file path for fuzzing.

  • Other options for fuzzing

You can get the full list of Eclipser's options and their descriptions by running the following command.

$ dotnet build/Eclipser.dll --help

Eclipser v2.0

Originally, Eclipser had its own simplified random-based fuzzing module, instead of relying on AFL. This was to support fuzzing multiple input sources (e.g. command-line arguments, standard input, and file input) within a single fuzzer run. We needed this feature for the comparison against KLEE on Coreutils benchmark, which was one of the main experimental targets in our paper.

However, as Eclipser is more often compared with other fuzzing tools, we abandon this feature and focus on fuzzing a single input source, as most fuzzers do. We also largely updated the command line interface of Eclipser accordingly. We note that you can still checkout v1.0 code from our repository to reproduce the Coreutils experiment result.

By focusing on fuzzing a single input source, we can now use AFL to perform random-based fuzzing. For this, from v2.0 Eclipser runs in parallel with AFL, as described above. This way, we can benefit from various features offered by AFL, such as source-based instrumentation, persistent mode, and deterministic mode. Still, the core architecture of Eclipser remains the same: it complements random-based fuzzing with our grey-box concolic testing technique.


To run the latest version of Eclipser, please use the Dockerfile provided in this repository. If you are interested in reproducing the results of ICSE 2019 paper, you can refer to Eclipser-Artifact repository, which uses Eclipser v0.1.

Supported Architectures

Eclipser currently supports x86 and x64 architecture binaries. We internally have a branch that supports ARM architecture, but do not plan to open source it. In default, Eclipser assumes that the target program is an x64 binary. If you want to fuzz an x86 binary, you should provide --architecture x86 option to Eclipser.


Please consider citing our paper (ICSE 2019):

  author = {Jaeseung Choi and Joonun Jang and Choongwoo Han and Sang Kil Cha},
  title = {Grey-box Concolic Testing on Binary Code},
  booktitle = {Proceedings of the International Conference on Software Engineering},
  pages = {736--747},
  year = 2019