CVE-2018-5739

Failure to release memory may exhaust system resources

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.

Remediation

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 security-officer@isc.org describing your storage setup and we will advise.

Category

6.5
CVSS
Severity: Medium
CVSS 3.0 •
CVSS 2.0 •
EPSS 3.27% Top 15%
Vendor Advisory isc.org
Affected: ISC Kea DHCP
Published at:
Updated at:

References

Link Tags
https://kb.isc.org/docs/aa-01626 vendor advisory

Frequently Asked Questions

What is the severity of CVE-2018-5739?
CVE-2018-5739 has been scored as a medium severity vulnerability.
How to fix CVE-2018-5739?
To fix CVE-2018-5739: Upgrade to Kea 1.4.0-P1 or higher, available via https://www.isc.org/downloads.
Is CVE-2018-5739 being actively exploited in the wild?
It is possible that CVE-2018-5739 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~3% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2018-5739?
CVE-2018-5739 affects ISC Kea DHCP.
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