Use-after-free vulnerability in the virNetMessageFree function in rpc/virnetserverclient.c in libvirt 1.0.x before 1.0.2, 0.10.2 before 0.10.2.3, 0.9.11 before 0.9.11.9, and 0.9.6 before 0.9.6.4 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code by triggering certain errors during an RPC connection, which causes a message to be freed without being removed from the message queue.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.