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Date: Fri, 27 Jun 2014 13:15:45 +0200
From: Petr Matousek <>
Subject: CVE request -- Linux kernel: sctp: sk_ack_backlog wrap-around problem

Description of the problem:
For a TCP-style socket, while processing the COOKIE_ECHO chunk in
sctp_sf_do_5_1D_ce(), after it has passed a series of sanity check, a
new association would be created in sctp_unpack_cookie(), but
afterwards, some processing maybe failed, and sctp_association_free()
will be called to free the previously allocated association, in
sctp_association_free(), sk_ack_backlog value is decremented for this
socket, since the initial value for sk_ack_backlog is 0, after
the decrement, it will be 65535, a wrap-around problem happens, and
if we want to establish new associations afterward in the same
socket, ABORT would be triggered since sctp deem the accept queue as

A remote attacker can block further connection to the particular sctp
server socket by sending a specially crafted sctp packet. 

Upstream patch:


Petr Matousek / Red Hat Product Security
PGP: 0xC44977CA 8107 AF16 A416 F9AF 18F3  D874 3E78 6F42 C449 77CA

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