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RFC 6946
Title: Processing of IPv6 "Atomic" Fragments
Author: F. Gont
Status: Standards Track
Stream: IETF
Date: May 2013
Mailbox: fg...@si6networks.com
Pages: 9
Characters: 18843
Updates: RFC 2460, RFC 5722
I-D Tag: draft-ietf-6man-ipv6-atomic-fragments-04.txt
URL: http://www.rfc-editor.org/rfc/rfc6946.txt
The IPv6 specification allows packets to contain a Fragment Header
without the packet being actually fragmented into multiple pieces (we
refer to these packets as "atomic fragments"). Such packets are
typically sent by hosts that have received an ICMPv6 "Packet Too Big"
error message that advertises a Next-Hop MTU smaller than 1280 bytes,
and are currently processed by some implementations as normal
"fragmented traffic" (i.e., they are "reassembled" with any other
queued fragments that supposedly correspond to the same original
packet). Thus, an attacker can cause hosts to employ atomic
fragments by forging ICMPv6 "Packet Too Big" error messages, and then
launch any fragmentation-based attacks against such traffic. This
document discusses the generation of the aforementioned atomic
fragments and the corresponding security implications. Additionally,
this document formally updates RFC 2460 and RFC 5722, such that IPv6
atomic fragments are processed independently of any other fragments,
thus completely eliminating the aforementioned attack vector.
This document is a product of the IPv6 Maintenance Working Group of the IETF.
This is now a Proposed Standard.
STANDARDS TRACK: This document specifies an Internet standards track
protocol for the Internet community,and requests discussion and suggestions
for improvements. Please refer to the current edition of the Internet
Official Protocol Standards (STD 1) for the standardization state and
status of this protocol. Distribution of this memo is unlimited.
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