The nscd service in the GNU C Library 2.3.4 onwards may crash due to a 
stack overflow when a malicious DNS server returns too large a response 
for a DNS query, resulting in degraded DNS resolution for the system.



Exploitation of this bug needs a system that has nscd enabled and using 
an untrusted DNS server for name resolution, with the compromised DNS 
server being capable of processing records large enough to result in a 
stack overflow in an nscd thread stack.  During experimentation, bind 9 
was unable to handle large records, but that could change in future or 
with a different name server.  In typical installations, nscd is 
executed in an isolated context as its own user without a shell, due to 
which any compromise of that service is isolated.



There is a remote possibility of nscd cache corruption if an attacker 
manages to get the stack pointer into a desired point in the heap, 
potentially resulting in other caches in nscd being overwritten with 
corrupt data through the stack overflow, until the buggy code path 
eventually results in a crash.



Finally, a crash in nscd may result in performance degradation when 
resolving names, but it does not result in a denial of service.