Sendmail Prescan Flaw May Let Remote Users Execute Arbitrary Code With Root Privileges
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SecurityTracker Alert ID: 1007734 |
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SecurityTracker URL: http://securitytracker.com/id/1007734
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CVE Reference:
CAN-2003-0694
(Links to External Site)
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Updated: Sep 17 2003
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Original Entry Date: Sep 17 2003
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Impact:
Execution of arbitrary code via local system, Execution of arbitrary code via network, Root access via local system, Root access via network
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): 8.12.9 and prior versions
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Description:
A vulnerability was reported in Sendmail. A local or remote user may be able to execute arbitrary code on the target system.
It is reported that the prescan() function in 'parseaddr.c' contains a flaw [that is different than previously reported prescan flaw]. The report states that various exploit methods are possible, but these exploit methods were not disclosed.
The report indicates that it is confirmed that a local user can exploit this flaw and it is believed that a remote user may also exploit this flaw.
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Impact:
A local or remote user may be able to execute arbitrary code with the privileges of the sendmail process.
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Solution:
The vendor has issued a fixed version (8.2.10), available at:
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.12.10.tar.gz
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.12.10.tar.gz.sig
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.12.10.tar.Z
ftp://ftp.sendmail.org/pub/sendmail/sendmail.8.12.10.tar.Z.sig
The following patch is also available:
http://sendmail.org/parse8.359.2.8.html
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Vendor URL: www.sendmail.org/8.12.10.html (Links to External Site)
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Cause:
Boundary error
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Underlying OS:
Linux (Any), UNIX (Any)
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Message History:
This archive entry has one or more follow-up message(s) listed below.
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Source Message Contents
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Date: Wed, 17 Sep 2003 11:19:46 +0200 (CEST)
Subject: [Full-Disclosure] Sendmail 8.12.9 prescan bug (a new one) [CAN-2003-0694]
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Hello lists,
--------
Overview
--------
There seems to be a remotely exploitable vulnerability in Sendmail up to
and including the latest version, 8.12.9. The problem lies in prescan()
function, but is not related to previous issues with this code.
The primary attack vector is an indirect invocation via parseaddr(),
although other routes are possible. Heap or stack structures, depending
on the calling location, can be overwritten due to the ability to go
past end of the input buffer in strtok()-alike routines.
This is an early release, thanks to my sheer stupidity.
--------------
Attack details
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Local exploitation on little endian Linux is confirmed to be trivial
via recipient.c and sendtolist(), with a pointer overwrite leading to a
neat case of free() on user-supplied data, i.e.:
eip = 0x40178ae2
edx = 0x41414141
esi = 0x61616161
SEGV in chunk_free (ar_ptr=0x4022a160, p=0x81337e0) at malloc.c:3242
0x40178ae2 <chunk_free+486>: mov %esi,0xc(%edx)
0x40178ae5 <chunk_free+489>: mov %edx,0x8(%esi)
Remote attack is believed to be possible.
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Workaround / fix
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Vendor was notified, and released an early patch attached below.
There are no known workarounds.
Index: parseaddr.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/parseaddr.c,v
retrieving revision 1.16
diff -u -r1.16 parseaddr.c
--- parseaddr.c 29 Mar 2003 19:44:01 -0000 1.16
+++ parseaddr.c 16 Sep 2003 17:37:26 -0000
@@ -700,7 +700,11 @@
addr[MAXNAME] = '\0';
returnnull:
if (delimptr != NULL)
+ {
+ if (p > addr)
+ p--;
*delimptr = p;
+ }
CurEnv->e_to = saveto;
return NULL;
}
--
------------------------- bash$ :(){ :|:&};: --
Michal Zalewski * [http://lcamtuf.coredump.cx]
Did you know that clones never use mirrors?
--------------------------- 2003-09-16 21:18 --
_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html
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