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Fetchmail Multidrop DoS
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SUMMARY
" <http://fetchmail.berlios.de/> Fetchmail is a full-featured, robust,
well-documented remote-mail retrieval and forwarding utility intended to
be used over on-demand TCP/IP links (such as SLIP or PPP connections). It
supports every remote-mail protocol now in use on the Internet: POP2,
POP3, RPOP, APOP, KPOP, all flavors of IMAP, ETRN, and ODMR. It can even
support IPv6 and IPSEC."
Lack of proper handling of header-less emails allow attackers to cause the
fetchmail to crash, effectively causing a DoS.
DETAILS
Vulnerable Systems:
* fetchmail version 6.2.5.4
* fetchmail version 6.3.0
Immune Systems:
* fetchmail version 6.3.1-rc1
* fetchmail version 6.3.1
* fetchmail version 6.2.5.5
Fetchmail contains a bug that causes an application to crash when
fetchmail is configured for multidrop mode and the upstream mail server
sends a message without headers. As fetchmail does not record this message
as "previously fetched", it will crash with the same message if it is
re-executed, so it cannot make progress. A malicious or broken-into
upstream server could thus cause a denial of service in fetchmail clients.
Workaround:
Where possible, singledrop mode may be an alternative.
Vendor Status:
The vendor has issued a fix: Download and install fetchmail 6.3.1 or a
newer stable release from fetchmail's project site at
<http://developer.berlios.de/project/showfiles.php?group_id=1824>
http://developer.berlios.de/project/showfiles.php?group_id=1824
The fix has also been back ported to the 6.2.5.5 legacy release which is
available from the same site.
Note however that 6.3.X has very few incompatible changes since 6.2.5.X so
6.3.X should be viable for most sites. It is therefore recommended that
every user and distributor upgrade to 6.3.1 or newer.
The fetchmail 6.2.5.X branch will be discontinued in early 2006.
The new 6.3.X stable branch has been available since 2005-11-30 and will
not change except for bugfixes, documentation and translations.
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-4348>
CVE-2005-4348
ADDITIONAL INFORMATION
The information has been provided by
<mailto:ma+bt@dt.e-technik.uni-dortmund.de> ma and bt .
The original article can be found at:
<http://fetchmail.berlios.de/fetchmail-SA-2005-03.txt>
http://fetchmail.berlios.de/fetchmail-SA-2005-03.txt
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