The platform we use is Windows 8.1, we use native SChannel and we 
don't have support for zlib compiled in. The problem does not occur 
when disabling encryption. having compression enabled seems to not 
cause any problem.

The crash happens at:
e_status = DecryptMessage( &m_context, &buffer_desc, 0, 0 );

in

int SChannel::decrypt( const std::string& data )

Hope this helps and thanks for fast reply.

Thanks for the report.
On which platform is this? Which encryption lib (OpenSSL, GNUTLS, 
Windows native SChannel, ...) do you use? Do you have support for zlib 
compiled in?
What happens if you disable encryption and/or compression?

ClientBase::setCompression( false );
ClientBase::setTls( TLSDisabled );

Disconnect will cause an access violation inside one of these three methods:

  m_connection->cleanup();
  m_encryption->cleanup();
  m_compression->cleanup();

The bug can be produced by creating a lot of clients and disconnect them all.

Example for producing the bug:

std::vector<std::shared_ptr<gloox::Client>> clients;

// create and connect n amount of clients (100 usually works)
for (int i = 0; i < n; i++)
{
        // generate a dummy user
        test_user_jid.setUsername("dummy_user_" + std::to_string(i));
        std::cout << "Creating user: " << test_user_jid.username() << std::endl;
        auto jabber_client = std::shared_ptr<gloox::Client>(new 
gloox::Client(test_user_jid, test_password));
        std::async(std::launch::async, [jabber_client]
        {
                auto connect_result = jabber_client->connect();
                if (connect_result)
                {
                        std::cout << jabber_client->jid().username() << " disconnected" << 
std::endl;
                }
        });

        clients.push_back(jabber_client);
}

std::cout << "Do some work (sleep)" << std::endl;
std::this_thread::sleep_for(std::chrono::milliseconds(1000));

// disconnect and delete all clients
for (auto itr = clients.begin(); itr != clients.end();)
{
        std::cout << "Deleting client for user: " << 
itr->get()->jid().username() << std::endl;
        itr->get()->disconnect();
        itr = clients.erase(itr);
}