Bug 1290292 (CVE-2015-5296) - CVE-2015-5296 samba: client requesting encryption vulnerable to downgrade attack
Summary: CVE-2015-5296 samba: client requesting encryption vulnerable to downgrade attack
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2015-5296
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1290706 1290707 1290708 1290709 1290710 1290711 1290727 1292069
Blocks: 1281327
TreeView+ depends on / blocked
 
Reported: 2015-12-10 05:29 UTC by Huzaifa S. Sidhpurwala
Modified: 2023-05-12 14:37 UTC (History)
15 users (show)

Fixed In Version: samba 4.1.22, samba 4.2.7, samba 4.3.3
Doc Type: Bug Fix
Doc Text:
A man-in-the-middle vulnerability was found in the way "connection signing" was implemented by Samba. A remote attacker could use this flaw to downgrade an existing Samba client connection and force the use of plain text.
Clone Of:
Environment:
Last Closed: 2016-01-08 12:19:30 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2016:0006 0 normal SHIPPED_LIVE Moderate: samba security update 2016-01-08 06:39:15 UTC
Red Hat Product Errata RHSA-2016:0010 0 normal SHIPPED_LIVE Moderate: samba4 security update 2016-01-08 03:43:17 UTC
Red Hat Product Errata RHSA-2016:0011 0 normal SHIPPED_LIVE Moderate: samba security update 2016-01-07 22:20:52 UTC
Red Hat Product Errata RHSA-2016:0015 0 normal SHIPPED_LIVE Moderate: samba security update 2016-01-08 15:18:26 UTC
Red Hat Product Errata RHSA-2016:0016 0 normal SHIPPED_LIVE Moderate: samba security update 2016-01-08 15:17:52 UTC

Description Huzaifa S. Sidhpurwala 2015-12-10 05:29:52 UTC 
As per upstream samba advisory:

Versions of Samba from 3.2.0 to 4.3.2 inclusive do not ensure that signing is negotiated when creating an encrypted client connection to
a server.

Without this a man-in-the-middle attack could downgrade the connection and connect using the supplied credentials as an unsigned, unencrypted
connection.

The following mitigation was suggested by upstream:


When using the smbclient command, always add the argument "--signing=required" when using the "-e" or "--encrypt" argument.

Alternatively, set the variable "client signing = mandatory" in the [global] section of the smb.conf file on any client using encrypted connections.

To protect a Samba server exporting encrypted shares against a downgrade attack set the variable "smb encrypt = mandatory" in the smb.conf definition of the encrypted shares.
Comment 1 Huzaifa S. Sidhpurwala 2015-12-10 06:34:11 UTC 
Acknowledgements:

Red Hat would like to thank the Samba project for reporting this issue. Upstream acknowledges Stefan Metzmacher of the Samba Team and Sernet.de as the original reporters.
Comment 5 Siddharth Sharma 2015-12-16 12:09:14 UTC 
Created samba tracking bugs for this issue:

Affects: fedora-all [bug 1292069]
Comment 6 Huzaifa S. Sidhpurwala 2015-12-17 04:12:27 UTC 
External References:

https://www.samba.org/samba/security/CVE-2015-5296.html
Comment 7 Tomas Hoger 2015-12-17 16:29:01 UTC 
Upstream commits:

https://git.samba.org/?p=samba.git;a=commitdiff;h=d724f835acb9f4886c0001af32cd325dbbf1f895
https://git.samba.org/?p=samba.git;a=commitdiff;h=1ba49b8f389eda3414b14410c7fbcb4041ca06b1
https://git.samba.org/?p=samba.git;a=commitdiff;h=a819d2b440aafa3138d95ff6e8b824da885a70e9
Comment 8 errata-xmlrpc 2016-01-07 17:07:00 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2016:0010 https://rhn.redhat.com/errata/RHSA-2016-0010.html
Comment 9 errata-xmlrpc 2016-01-07 17:23:21 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2016:0011 https://rhn.redhat.com/errata/RHSA-2016-0011.html
Comment 10 errata-xmlrpc 2016-01-08 01:40:31 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2016:0006 https://rhn.redhat.com/errata/RHSA-2016-0006.html
Comment 11 errata-xmlrpc 2016-01-08 10:19:12 UTC 
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.1 for RHEL 7

Via RHSA-2016:0016 https://rhn.redhat.com/errata/RHSA-2016-0016.html
Comment 12 errata-xmlrpc 2016-01-08 10:19:56 UTC 
This issue has been addressed in the following products:

  Red Hat Gluster Storage 3.1 for RHEL 6

Via RHSA-2016:0015 https://rhn.redhat.com/errata/RHSA-2016-0015.html
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