Bug 948072 (CVE-2013-1923)

Summary: CVE-2013-1923 nfs-utils: rpc.gssd is vulnerable to DNS spoofing
Product: [Other] Security Response Reporter: Vincent Danen <vdanen>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: bfields, jkurik, jlieskov, rmainz, security-response-team, steved
Target Milestone: ---Keywords: Reopened, Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: impact=low,public=20130402,reported=20130403,source=redhat,cvss2=3.2/AV:A/AC:H/Au:N/C:P/I:P/A:N,rhel-5/nfs-utils=wontfix,rhel-6/nfs-utils=wontfix,fedora-all/nfs-utils=affected
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-08-22 02:24:20 EDT Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
Bug Depends On: 948078    
Bug Blocks: 948077    

Description Vincent Danen 2013-04-03 18:27:44 EDT
It was reported [1],[2] that rpc.gssd in nfs-utils is vulnerable to DNS spoofing due to it depending on PTR resolution for GSSAPI authentication.  Because of this, if a user where able to poison DNS to a victim's computer, they would be able to trick rpc.gssd into talking to another server (perhaps with less security) than the intended server (with stricter security).  If the victim has write access to the second (less secure) server, and the attacker has read access (when they normally might not on the secure server), the victim could write files to that server, which the attacker could obtain (when normally they would not be able to).  To the victim this is transparent because the victim's computer asks the KDC for a ticket to the second server due to reverse DNS resolution; in this case Krb5 authentication does not fail because the victim is talking to the "correct" server.

A patch that prevents this issue has been posted [3].

To workaround this issue, set the IP/host pair in /etc/hosts so that it cannot be spoofed.

A good explanation is also available here [4].

[1] http://marc.info/?l=linux-nfs&m=136491998607561&w=2
[2] http://marc.info/?l=linux-nfs&m=136500502805121&w=2
[3] http://marc.info/?l=linux-nfs&m=136493115612397&w=2
[4] http://ssimo.org/blog/id_015.html
Comment 1 Vincent Danen 2013-04-03 18:42:01 EDT
Created nfs-utils tracking bugs for this issue

Affects: fedora-all [bug 948078]
Comment 2 Vincent Danen 2013-04-04 16:52:47 EDT
This was assigned CVE-2013-1923:

http://www.openwall.com/lists/oss-security/2013/04/04/5
Comment 7 Vincent Danen 2014-01-11 14:34:33 EST
Current Fedora 19+ ship with nfs-utils 1.2.8 which includes the fix.
Comment 9 Vincent Danen 2015-08-22 02:23:58 EDT
Statement:

Red Hat Product Security has rated this issue as having Low security impact. This issue is not currently planned to be addressed in future updates. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.