libssh2: libssh2: Denial of Service via integer underflow in AES-GCM cipher negotiation

A flaw was found in libssh2. A pre-authentication integer underflow vulnerability exists in the ssh2ciphercrypt function when negotiating AES-GCM ciphers during the handshake. A malicious SSH server can exploit this to trigger an out-of-bounds read and a memory copy operation with an extremely...