MDKSA-2002:030 - temporary fix for netfilter information leak

From: Mandrake Linux Security Team (security@linux-mandrake.com)
Date: Thu May 09 2002 - 09:41:48 PDT

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    ________________________________________________________________________
    
                    Mandrake Linux Security Update Advisory
    ________________________________________________________________________
    
    Package name:           iptables/kernel
    Advisory ID:            MDKSA-2002:030
    Date:                   May 9th, 2002
    Affected versions:      8.0, 8.1, 8.2
    ________________________________________________________________________
    
    Problem Description:
    
     A problem was discovered with Netfilter Network Address Translation
     (NAT) capabilities.  It was found that iptables can leak information
     about how port forwarding is accomplished in unfiltered ICMP packets.
     When a NAT rule applies to the first packet of a connection, which
     subsequently causes the system to generate an ICMP error message, the
     ICMP error message is transmitted including the translated address.
     This information gives the IP address of the system to which the
     connection would have been forwarded had the error message not been
     generated, exposing information about the netfilter configuration and
     the network topology.
    
     There is currently no clean fix for this problem, but a fix is being
     worked on.  In the meantime, if you use the NAT capabilities of
     iptables, you can protect yourself by filtering out untracked local
     ICMP packets using the following iptables command:
    
       iptables -A OUTPUT -m state -p icmp --state INVALID -j DROP
    
     All kernel patches from iptables < 1.2.6a are vulnerable.  All kernel
     versions from 2.4.4 and up to (at least) 2.4.19-pre6 use a vulnerable
     version.  Thanks to Philippe Biondi for discovering this problem.
    ________________________________________________________________________
    
    References:
    
      http://online.securityfocus.com/archive/1/271530/2002-05-06/2002-05-12/0
    ________________________________________________________________________
    
    Updated Packages:
    
      None currently available.
    ________________________________________________________________________
    
    Bug IDs fixed (see https://qa.mandrakesoft.com for more information):
    
    ________________________________________________________________________
    
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      security@linux-mandrake.com
    ________________________________________________________________________
    
    Type Bits/KeyID     Date       User ID
    pub  1024D/22458A98 2000-07-10 Linux Mandrake Security Team
      <security@linux-mandrake.com>
    
    
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