Oracle has admitted that a potentially devastating security flaw could allow crackers to mount successful denial of service attacks on NT servers running its database software.
For Oracle on Windows NT, the Oracle listener process redirects connection requests to a new port and the Oracle database server creates a new thread for this port.
If a connection to the port is not made, the thread and consumed memory is lost until the server is restarted.
Because of this, if an attacker repeatedly requests redirects which aren't completed, all the memory on the server will be consumed and legitimate users will be blocked.
After this, any attempt to log in to the console results in the dreaded Blue Screen of Death and the need to reboot a system.
Internet Security Systems, whose X-Force security research team discovered the flaw, have suggested a workaround which involves using a feature called "valid node checking" on Oracle Net8 (formerly Oracle SQL*Net). This can be used to allow or deny access to Oracle server processes from network clients with specified IP addresses. More information on this is available here.
ISS has also identified four forms of denial of service attacks against the Oracle listener service that affect software working on Unix platforms. These vulnerabilities, details of which are available here, could allow an unauthenticated user to prevent other users from connecting to a database.
Oracle has produced a series of software patches to guard against the flaws that appear likely to be more difficult to exploit, and cause less damage, than the NT bug but this is so far unclear. ®
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