CVE-2015-5296: Input Validation
First published: Thu Dec 10 2015(Updated: )
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.
Credit: secalert@redhat.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| redhat/samba | <4.1.22 | 4.1.22 |
| redhat/samba | <4.2.7 | 4.2.7 |
| redhat/samba | <4.3.3 | 4.3.3 |
| Samba | >=3.2.0<4.1.22 | |
| Samba | >=4.2.0<4.2.7 | |
| Samba | >=4.3.0<4.3.3 | |
| Debian GNU/Linux | =7.0 | |
| Debian GNU/Linux | =8.0 | |
| Ubuntu Linux | =12.04 | |
| Ubuntu Linux | =14.04 | |
| Ubuntu Linux | =15.04 | |
| Ubuntu Linux | =15.10 |
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Reference Links
- http://lists.fedoraproject.org/pipermail/package-announce/2015-December/174076.html
- http://lists.fedoraproject.org/pipermail/package-announce/2015-December/174391.html
- http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00019.html
- http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00020.html
- http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00032.html
- http://lists.opensuse.org/opensuse-security-announce/2015-12/msg00033.html
- http://lists.opensuse.org/opensuse-security-announce/2016-01/msg00002.html
- http://lists.opensuse.org/opensuse-security-announce/2016-01/msg00017.html
- http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00042.html
- http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00047.html
- http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00048.html
- http://www.debian.org/security/2016/dsa-3433
- http://www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
- http://www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html
- http://www.securityfocus.com/bid/79732
- http://www.securitytracker.com/id/1034493
- http://www.ubuntu.com/usn/USN-2855-1
- http://www.ubuntu.com/usn/USN-2855-2
- https://bugzilla.redhat.com/show_bug.cgi?id=1290292
- https://git.samba.org/?p=samba.git;a=commit;h=1ba49b8f389eda3414b14410c7fbcb4041ca06b1
- https://git.samba.org/?p=samba.git;a=commit;h=a819d2b440aafa3138d95ff6e8b824da885a70e9
- https://git.samba.org/?p=samba.git;a=commit;h=d724f835acb9f4886c0001af32cd325dbbf1f895
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05115993
- https://security.gentoo.org/glsa/201612-47
- https://www.samba.org/samba/security/CVE-2015-5296.html
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1292069
- 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
- https://rhn.redhat.com/errata/RHSA-2016-0010.html
- https://rhn.redhat.com/errata/RHSA-2016-0011.html
- https://rhn.redhat.com/errata/RHSA-2016-0006.html
- https://rhn.redhat.com/errata/RHSA-2016-0016.html
- https://rhn.redhat.com/errata/RHSA-2016-0015.html
- https://git.samba.org/?p=samba.git%3Ba=commit%3Bh=a819d2b440aafa3138d95ff6e8b824da885a70e9
- https://git.samba.org/?p=samba.git%3Ba=commit%3Bh=1ba49b8f389eda3414b14410c7fbcb4041ca06b1
- https://git.samba.org/?p=samba.git%3Ba=commit%3Bh=d724f835acb9f4886c0001af32cd325dbbf1f895
Frequently Asked Questions
What is the severity of CVE-2015-5296?
CVE-2015-5296 is classified as a medium severity vulnerability due to potential man-in-the-middle attacks.
How do I fix CVE-2015-5296?
To fix CVE-2015-5296, upgrade Samba to version 4.1.22 or later, 4.2.7 or later, or 4.3.3 or later.
What versions of Samba are affected by CVE-2015-5296?
Samba versions from 3.2.0 to 4.3.2 inclusive are affected by CVE-2015-5296.
What kind of attack does CVE-2015-5296 allow?
CVE-2015-5296 allows a man-in-the-middle attack due to improper signing negotiation during encrypted connections.
Is there any workaround for CVE-2015-5296?
The primary recommendation is to update to the patched versions; there are no reliable workarounds for CVE-2015-5296.
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