IPv4-Mapped Addresses on the Wire Considered Harmful

Document Type Expired Internet-Draft (individual)
Last updated 2003-10-23
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The IPv6 Addressing Architecture [Hinden, 1998] defines the 'IPv4-mapped IPv6 address.' These addresses are used in the IPv6 basic API [Gilligan, 1999] to denote IPv4 addresses using AF_INET6 sockets. These addresses are used in protocol proposals such as SIIT [Nordmark, 2000] to denote IPv6 communication using AF_INET6 sockets. Therefore, IPv4-mapped addresses have two different meanings, and they are not distinguishable from the user-land applications. This draft discusses security threats due to this ambiguity of IPv4-mapped address. It also discusses threats due to the additional complexities introduced by IPv4-mapped addresses. Finally, it proposes to resolve these problems by forbidding protocols from using IPv4-mapped addresses for IPv6 communications.


Christopher Metz (cmetz@vnet.ibm.com)
Jun-ichiro Itoh (itojun@iijlab.net)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)