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DROWN Scanner

Important: Some versions of this tool produce the following lines on startup:

Import Error - most likely due to missing pycrypto libaries - disabling crypto functionality
ImportError('cannot import name TLSHandshake',)

These lines do not prevent the tool from producing correct results.

Learn more here:

This python utility scans for vulnerability to the DROWN attack against TLS. It is distributed under the GPLv2 license, and includes a specific version of (which is also distributed under GPLv2) and We are grateful to both authors for providing these useful libraries.

This utility was written in an ad-hoc manner in order to identify only the most common vulnerable configurations. We emphasize that it cannot accurately detect all vulnerable servers, and no one should rely on it to confidently determine a particular server is not vulnerable.

In particular, the utility only detects SSLv2 support by a single port. DROWN is made worse by its cross-protocol nature, i.e. an HTTPS server that doesn't support SSLv2 may be vulnerable because it shares its public key with an SMTP server that does. This utility cannot detect this scenario, and we strongly recommend testing servers using our online scanner, at

Likewise, it may also have false positives, i.e. it may indicate a server is vulnerable when it is in fact not.

Hubert Kario has also made different scanning scripts available here:


You need the packages listed below. This dependency list is unfortunately a work in progress. If you think you're missing a dependency, please read the instructions for other operating systems, and see if they might shed light on the issue. Pull requests clarifying the dependency list (and also general PRs) are welcome.

On a Debian system:

sudo apt-get install tcpdump python-pyasn1 scapy python-crypto python-pip

On Debian Jessie also install

sudo apt-get install python-enum

and for all Debian versions, also run

sudo pip install scapy-ssl_tls

On a Fedora/RHEL system:

sudo yum install python-enum scapy python-crypto tcpdump

and also run sudo pip install scapy-ssl_tls

Or generally with pip:

sudo pip install enum pycrypto scapy pyasn1 scapy-ssl_tls


Some users have encountered problems on CentOS with the asn1 package (or in general). In addition to installing the above dependencies for Fedora/RHEL, please see this issue for a suggested solution:

Mac users

You may also need dnet as a dependency.


The latest version of Scapy supports Windows out-of-the-box, with Python 2.6. See here for installation instructions:

And here if you absolutely need to use Python 2.7:

Even more dependencies

One user has graciously documented setting up the dependencies on a stripped-down installation of CentOS:


docker build -t public-drown-scanner .
docker run -it public-drown-scanner localhost 443


Short version: use python libdnet from ports and install everything else inside a virtualenv.

Long version:

sudo pkg install py27-virtualenv libdnet py27-libdnet
git clone
cd public_drown_scanner
virtualenv --system-site-packages .
bin/pip install enum pycrypto scapy pyasn1 scapy-ssl_tls pcapy

Usage examples:

python localhost 443
python localhost 587 -esmtp
python localhost 143 -imap
python localhost 25 -esmtp
python localhost 110 -pop3
python localhost 443 -bare