Bug 1702541 (CVE-2018-5743)

Summary: CVE-2018-5743 bind: Limiting simultaneous TCP clients is ineffective
Product: [Other] Security Response Reporter: Huzaifa S. Sidhpurwala <huzaifas>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact: Petr Sklenar <psklenar>
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anon.amish, apmukher, dawwu, jlyle, jpopelka, mruprich, msehnout, mvanderw, pemensik, pzhukov, security-response-team, thozza, vonsch, yozone, zdohnal
Target Milestone: ---Keywords: Reopened, Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: bind 9.11.6-P1, bind 9.12.4-P1, bind 9.14.1, bind 9.11.7 Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the way bind implemented tunable which limited simultaneous TCP client connections. A remote attacker could use this flaw to exhaust the pool of file descriptors available to named, potentially affecting network connections and the management of files such as log files or zone journal files. In cases where the named process is not limited by OS-enforced per-process limits, this could additionally potentially lead to exhaustion of all available free file descriptors on that system.
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-07-12 13:07:03 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1702554, 1702555, 1702556, 1702557, 1702558, 1702881, 1702882, 1744468, 1744469    
Bug Blocks: 1702542    
Attachments:
Description Flags
bind patch against 9.11.6
none
patch for 9.12.4
none
patch for 9.14.1 none

Description Huzaifa S. Sidhpurwala 2019-04-24 05:29:40 UTC
As per upstream advisory:

By design, BIND is intended to limit the number of TCP clients that can be connected at any given time. The number of allowed connections is a tunable parameter which, if unset, defaults to a conservative value for most servers. Unfortunately, the code which was intended to limit the number of simultaneous connections contains an error which can be exploited to grow the number of simultaneous connections beyond this limit.

By exploiting the failure to limit simultaneous TCP connections,an attacker can deliberately exhaust the pool of file descriptors available to named, potentially affecting network connections and the management of files such as log files or zone journal files.

In cases where the named process is not limited by OS-enforced per-process limits, this could additionally potentially lead to exhaustion of all available free file descriptors on that system.

Comment 1 Huzaifa S. Sidhpurwala 2019-04-24 05:29:42 UTC
Acknowledgments:

Name: ISC
Upstream: AT&T

Comment 2 Huzaifa S. Sidhpurwala 2019-04-24 06:15:08 UTC
Created attachment 1557974 [details]
bind patch against 9.11.6

Comment 3 Huzaifa S. Sidhpurwala 2019-04-24 06:15:42 UTC
Created attachment 1557975 [details]
patch for 9.12.4

Comment 4 Huzaifa S. Sidhpurwala 2019-04-24 06:16:13 UTC
Created attachment 1557976 [details]
patch for 9.14.1

Comment 10 Huzaifa S. Sidhpurwala 2019-04-25 05:22:57 UTC
External References:

https://kb.isc.org/docs/cve-2018-5743

Comment 11 Huzaifa S. Sidhpurwala 2019-04-25 05:23:15 UTC
Created bind tracking bugs for this issue:

Affects: fedora-all [bug 1702881]


Created bind99 tracking bugs for this issue:

Affects: fedora-all [bug 1702882]

Comment 13 Petr Menšík 2019-05-07 14:02:51 UTC
Useful resource explaining how this CVE fix works and how is different from previous versions, is available on upstream KB[1].

1. https://kb.isc.org/docs/how-does-tcp-clients-work

Comment 15 errata-xmlrpc 2019-05-13 05:04:50 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2019:1145 https://access.redhat.com/errata/RHSA-2019:1145

Comment 17 errata-xmlrpc 2019-05-29 18:08:12 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2019:1294 https://access.redhat.com/errata/RHSA-2019:1294

Comment 23 errata-xmlrpc 2019-06-17 12:48:14 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2019:1492 https://access.redhat.com/errata/RHSA-2019:1492

Comment 24 Huzaifa S. Sidhpurwala 2019-06-19 04:47:31 UTC
Statement:

This bind flaw can be exploited by a remote attacker (AV:N) by opening large number of  simultaneous TCP client connections with the server. No special exploit code is required apart from the ability to open large number of TCP connections simultaneously either from one attacker machine or via some distributed attacker network (AC:L and PR:L). No user interaction is required from the server side (UI:N). The attacker can cause denial of service (A:H) by exhausting the file descriptor pool which named has access to. Also in cases where named process is not limited by OS-enforced per-process limits, this could cause exhaustion of available free file descriptors on the system running the named server causing denial of service for other processes running on that machine (S:C).

Comment 25 Product Security DevOps Team 2019-07-12 13:07:03 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2018-5743

Comment 26 msiddiqu 2019-08-22 07:58:26 UTC
Release notes mentioning CVE-2018-5743 fix:

Experimental development branch
9.15.3: https://downloads.isc.org/isc/bind9/9.15.3/RELEASE-NOTES-bind-9.15.3.html

Comment 28 errata-xmlrpc 2019-09-10 13:46:31 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.4 Extended Update Support

Via RHSA-2019:2698 https://access.redhat.com/errata/RHSA-2019:2698

Comment 30 errata-xmlrpc 2019-10-08 10:00:16 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.5 Extended Update Support

Via RHSA-2019:2977 https://access.redhat.com/errata/RHSA-2019:2977