Public Date:
1702541: CVE-2018-5743 bind: Limiting simultaneous TCP clients is ineffective
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.

Find out more about CVE-2018-5743 from the MITRE CVE dictionary dictionary and NIST NVD.


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).

CVSS v3 metrics

CVSS3 Base Score 8.6
CVSS3 Base Metrics CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Changed
Confidentiality None
Integrity Impact None
Availability Impact High

Red Hat Security Errata

Platform Errata Release Date
Red Hat Enterprise Linux 6 (bind) RHSA-2019:1492 2019-06-17
Red Hat Enterprise Linux 8 (bind) RHSA-2019:1145 2019-05-13
Red Hat Enterprise Linux Extended Update Support 7.4 (bind) RHSA-2019:2698 2019-09-12
Red Hat Enterprise Linux 7 (bind) RHSA-2019:1294 2019-05-29

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 5 bind97 Out of support scope
Red Hat Enterprise Linux 5 bind Out of support scope
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.


Red Hat would like to thank ISC for reporting this issue. Upstream acknowledges AT&T as the original reporter.

External References

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