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Bug 186057 - CVE-2006-1242 Linux zero IP ID vulnerability?
Summary: CVE-2006-1242 Linux zero IP ID vulnerability?
Alias: None
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: kernel
Version: 4.0
Hardware: All
OS: Linux
Target Milestone: ---
: ---
Assignee: Thomas Graf
QA Contact: Brian Brock
Whiteboard: impact=low,source=bugtraq,reported=20...
Depends On:
Blocks: 181409
TreeView+ depends on / blocked
Reported: 2006-03-21 13:10 UTC by Marcel Holtmann
Modified: 2014-06-18 08:28 UTC (History)
4 users (show)

Fixed In Version: RHSA-2006-0575
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2006-08-10 22:50:06 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2006:0575 normal SHIPPED_LIVE Important: Updated kernel packages available for Red Hat Enterprise Linux 4 Update 4 2006-08-10 04:00:00 UTC

Description Marcel Holtmann 2006-03-21 13:10:06 UTC
Interesting behaviour of some Linux kernels that may be exploited by a remote
attacker to abuse the ID field of IP packets, effectively bypassing the zero IP
ID in DF packets countermeasure implemented since 2.4.8 (IIRC).

Comment 1 David Miller 2006-03-22 20:47:35 UTC
The code paths for sending TCP packets when we have a socket and when
we don't have one are different, and in fact this is unavoidable.

When we send a reset because we don't have a TCP socket that matches,
we have to use tcp_v4_send_reset(), which uses the ip_send_reply()
framework using the system-wide "tcp_socket" that is used for sending
packets when we have no associated socket.

SYN+ACK responses, go through yet another interface, ip_build_and_send_pkt()
via tcp_v4_send_synack().

We could pass a flag into ip_build_and_send_pkt() to tell it to not use a
non-zero IP ID when the DF bit is set.  Actually, scratch that, it should be
using the function "ip_select_ident_more()" just like ip_build_xmit() does.

That would solve the problem.

FWIW I don't see this as much of a real security problem, and by fixing it
we'll make Linux versions even more specifically identifyable remotely :)

Comment 2 Marcel Holtmann 2006-03-23 09:02:12 UTC
According to Chris Wright the latest vanilla kernel contains a fix for it:;a=commit;h=1a55d57b107c3e06935763905dc0fb235214569d

Comment 3 David Miller 2006-03-23 09:16:36 UTC
Right, I pushed that to 2.6.17 and 2.6.x -stable.

Vanilla 2.4.x does not have the problem, but our RHEL3 2.4.x does
because it contains the IPSEC backport.

Comment 4 Thomas Graf 2006-03-24 14:34:12 UTC
RHEL4 is not vulnerable to this with the default firewall enabled, at least not
the case documented. Naturally we should include the fix for cases where it is

Comment 7 Jason Baron 2006-04-07 01:52:30 UTC
committed in stream U4 build 34.14. A test kernel with this patch is available

Comment 8 Bob Johnson 2006-04-11 17:13:34 UTC
This issue is on Red Hat Engineering's list of planned work items 
for the upcoming Red Hat Enterprise Linux 4.4 release.  Engineering 
resources have been assigned and barring unforeseen circumstances, Red 
Hat intends to include this item in the 4.4 release.

Comment 10 Mike Gahagan 2006-07-14 21:09:22 UTC
Patch is in -42.EL.

Comment 12 Red Hat Bugzilla 2006-08-10 22:50:07 UTC
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

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