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Category:   Application (E-mail Server)  >   Sendmail Vendors:   Sendmail Consortium
Sendmail 'check_relay' E-mail Access Control Features Can Be Bypassed By Remote Users
SecurityTracker Alert ID:  1005748
SecurityTracker URL:  http://securitytracker.com/id/1005748
CVE Reference:   CVE-2002-2261   (Links to External Site)
Updated:  Jun 8 2008
Original Entry Date:  Dec 4 2002
Impact:   Host/resource access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): 8.9, 8.12
Description:   An access control vulnerability was reported in Sendmail. A remote user with the ability to control a DNS server or spoof the DNS may be able to bypass a target server's sendmail access controls and send mail to or via that server.

It is reported that a remote user can bypass the access restrictions imposed via the 'check_relay' function by using bogus domain name system (DNS) data. It appears that a remote user with control of a DNS server can supply a blank client name via DNS to cause the 'check_relay' hostname access controls to fail to block mail from that domain.

Sendmail.org credits Kai Schlichting with reporting this flaw.

Impact:   A remote user with ability to spoof the DNS can bypass sendmail access restrictions and send mail to or via the server.
Solution:   The vendor has released the following patches.

For 8.12:

http://www.sendmail.org/patches/proto.m4.8.649.2.13

For 8.9:

http://www.sendmail.org/patches/proto.m4.8.9.3

According to the vendor version 8.12.7 will contain a patch to correct this flaw.

Also, if your system is configured to use the FEATURE(`delay_checks'), then the vendor says that you do not need a patch.

Vendor URL:  www.sendmail.org/ (Links to External Site)
Cause:   Access control error, State error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   This archive entry has one or more follow-up message(s) listed below.
Dec 10 2009 (HP Issues Fix) Sendmail 'check_relay' E-mail Access Control Features Can Be Bypassed By Remote Users
HP has issued a fix for HP-UX 11.11 and 11.23.



 Source Message Contents

Subject:  Bypassing Sendmail access restrictions


Sendmail.org reports that access restrictions imposed via 'check_relay' for IP addresses 
can be circumvented using bogus DNS data.  The following patches are available:

For 8.12:

  http://www.sendmail.org/patches/proto.m4.8.649.2.13

For 8.9:

  http://www.sendmail.org/patches/proto.m4.8.9.3

Sendmail.org credits Kai Schlichting with reporting this flaw.

According to the vendor version 8.12.7 will contain a patch to correct this flaw.  Also,
if your system is configured to use the FEATURE(`delay_checks'), then the vendor says that
you do not need a patch.



 
 


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