Common Vulnerabilities and Exposures assigned an identifier CVE-2007-5729 to the following vulnerability:

The NE2000 emulator in QEMU 0.8.2 allows local users to execute arbitrary code by writing Ethernet frames with a size larger than the MTU to the EN0_TCNT register, which triggers a heap-based buffer overflow in the slirp library, aka NE2000 
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mtu
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 heap overflow.  NOTE: some sources have used CVE-2007-1321 to refer to this issue as part of 
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NE2000 network driver and the socket code,
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 but this is the correct identifier for the mtu overflow vulnerability.

References:

http://taviso.decsystem.org/virtsec.pdf
http://www.debian.org/security/2007/dsa-1284