Title: Buffer Overruns in SQL Server 2000 Resolution Service
Could Enable Code Execution (Q323875)
Date: 24 July 2002
Software: SQL Server 2000
Impact: Three vulnerabilities, the most serious of which could
enable an attacker to gain control over an affected
SQL Server 2000 installation
Max Risk: Critical
Bulletin: MS02-039
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-039.asp.
SQL Server 2000 introduces the ability to host multiple instances of
SQL Server on a single physical machine. Each instance operates for
all intents and purposes as though it was a separate server. However,
the multiple instances cannot all use the standard SQL Server session
port (TCP 1433). While the default instance listens on TCP port 1433,
named instances listen on any port assigned to them. The SQL Server
Resolution Service, which operates on UDP port 1434, provides a way
for clients to query for the appropriate network endpoints to use for
a particular SQL Server instance.
There are three security vulnerabilities here. The first two are
buffer overruns. By sending a carefully crafted packet to the
Resolution Service, an attacker could cause portions of system memory
(the heap in one case, the stack in the other) to be overwritten.
Overwriting it with random data would likely result in the failure of
the SQL Server service; overwriting it with carefully selected data
could allow the attacker to run code in the security context of the
SQL Server service.
The third vulnerability is a denial of service vulnerability. SQL
uses a keep-alive mechanism to distinguish between active and passive
instances. It is possible to create a keep-alive packet that, when
sent to the Resolution Service, will cause SQL Server 2000 to respond
with the same information. An attacker who created such a packet,
spoofed the source address so that it appeared to come from a one SQL
Server 2000 system, and sent it to a neighboring SQL Server 2000
system could cause the two systems to enter a never-ending cycle of
keep-alive packet exchanges. This would consume resources on both
systems, slowing performance considerably.
Buffer Overruns in SQL Server Resolution Service:
Denial of Service via SQL Server Resolution Service:
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