The NBD Tools are the Network Block Device utilities allowing one to use remote block devices over a TCP/IP network. It includes a userland NBD server.
Kurt Fitzner discovered that the NBD server allocates a request buffer that fails to take into account the size of the reply header.
A remote attacker could send a malicious request that can result in the execution of arbitrary code with the rights of the NBD server.
There is no known workaround at this time.
All NBD Tools users should upgrade to the latest version:
# emerge --sync # emerge --ask --oneshot --verbose ">=sys-block/nbd-2.8.2-r1"