Given this code is not in any released versions, no security release has been issued. Missing allocation check in sftp server processing read requests may cause NULL dereference on low-memory conditions. The malicious client can request up to 4GB SFTP reads, causing allocation of up to 4GB buffers, which is being unchecked for failure. This will likely crash the authenticated user sftp server's connection (if implemented as forking as we recommend). For thread-based servers, this might cause DoS also for legitimate users.