CVE-2018-5739

Failure to release memory may exhaust system resources

6.5MediumCVSS base score
1.9%Exploitation in 30 daysEPSS · top 20% of all CVEs
NoKnown exploitednot in CISA's KEV catalog
NonePublic exploitsnone known yet

Published: 16 Jan 2019
Updated: 17 Sept 2024
Reserved: 17 Jan 2018
Assigned by: isc
NVD status: Modified

Weakness

Only servers using hooks which make use of the callout handle store are affected. A Kea server which is using one or more hooks libraries that exhibit this problem will increase its memory use over time, with the rate of increase being proportional to the amount of DHCP traffic processed. Eventually, due to uncontrolled growth, the server will either exhaust all system memory or, if the administrator has set a per-process memory limit, will hit that limit, after which point further memory allocations will fail and the Kea server will crash. An attacker who is within the broadcast domain of the Kea server or in a network which is permitted to relay DHCP traffic to the Kea server can hasten the arrival of this outcome by deliberately sending a large volume of requests to the Kea server. Ability to deliberately trigger this vulnerability depends on the hooks libraries used and the hook points used for callouts. Our scoring for this vulnerability is based on the hook points used for hook libraries distributed by ISC and also based on the assumption that the Kea server does not accept arbitrary traffic from the internet (but is protected, e.g. by firewall, and only accepts DHCP traffic from the local broadcast domain and from nearby networks via authorized DHCP relay agents.) We cannot score every combination, but the risk could be higher to custom-developed hook libraries using other hook points or to servers which accept arbitrary DHCP traffic without restriction.
CWE-772

Description

An extension to hooks capabilities which debuted in Kea 1.4.0 introduced a memory leak for operators who are using certain hooks library facilities. In order to support multiple requests simultaneously, Kea 1.4 added a callout handle store but unfortunately the initial implementation of this store does not properly free memory in every case. Hooks which make use of query4 or query6 parameters in their callouts can leak memory, resulting in the eventual exhaustion of available memory and subsequent failure of the server process. Affects Kea DHCP 1.4.0.

Timeline

2018
17 Jan 2018
17 Jan 2018
ID reserved
By isc
2019
16 Jan 201912 months later
16 Jan 2019· 12 months later
Published
2024
17 Sept 20246 years later
17 Sept 2024· 6 years later
Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2018-5739, by who scored it
Scored by	CVSS	Score	Vector
iscCNA (assigner)	3.0	Medium6.5	CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified	3.0	High7.5	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS (exploitation in 30 days): 1.9% · top 20% of all CVEs (11 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.

Affected products

ISC · Kea DHCP
- affected Kea DHCP 1.4.0

What to do

Solution: Upgrade to Kea 1.4.0-P1 or higher, available via https://www.isc.org/downloads.

Workaround: + Monitoring and routinely restarting ISC Kea DHCPv4 and DHCPv6 services may be an effective mitigation for some production environments + Running a new build of Kea without any hook libraries that use the callout store is another option, though it may not be a viable option where the production environment is dependent on the other hooks that need to be omitted to avoid these symptoms. These hooks distributed by ISC do not use the callout store and are safe to use: Lease Commands, Stat Commands, Host Commands (a Kea Premium hook) and Subnet Commands (a subscriber-only hook provided to Kea support customers). + Reverting to Kea DHCP 1.3.0 may be possible for some production environments but because of differences in the database schema operators should check carefully before attempting rollback: - If using memfile storage entirely, there should not be any compatibility issues. - If using a database solution for hosts or leases, the 1.4.0 schema will be incompatible with ISC Kea 1.3.0; the database therefore must be restored from a pre-upgrade backup for this to be successful. - If you are unsure whether or not you can roll back to 1.3.0 without restoring a previous version of your database, you may send an e-mail to [email protected] describing your storage setup and we will advise.

References

https://kb.isc.org/docs/aa-01626 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated 17 Sept 2024, 02:11 UTC.