What’s Vulnerable › Vulnerabilities

CVE-2018-5733: A malicious client can overflow a reference counter in ISC dhcpd

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 20.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-01-16 · updated 2026-06-17
• Weakness: CWE-190

Description

A malicious client which is allowed to send very large amounts of traffic (billions of packets) to a DHCP server can eventually overflow a 32-bit reference counter, potentially causing dhcpd to crash. Affects ISC DHCP 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0.

Affected products

• Canonical Ubuntu Linux: 14.04, 16.04, 17.10
• Debian Linux: 7.0, 8.0, 9.0
• ISC DHCP: from 4.2.0 through 4.2.8; from 4.3.0 through 4.3.6; 4.1-esv, 4.1-esv-r1, 4.1-esv-r10, 4.1-esv-r10_b1, 4.1-esv-r10_rc1, 4.1-esv-r11 (+30)
• RedHat Enterprise Linux Desktop: 6.0, 7.0
• RedHat Enterprise Linux Server: 6.0, 7.0
• RedHat Enterprise Linux Server Aus: 7.4, 7.6
• RedHat Enterprise Linux Server Eus: 7.4, 7.5, 7.6
• RedHat Enterprise Linux Workstation: 6.0, 7.0

References

• http://www.securityfocus.com/bid/103188
• http://www.securitytracker.com/id/1040437
• https://access.redhat.com/errata/RHSA-2018:0469
• https://access.redhat.com/errata/RHSA-2018:0483
• https://kb.isc.org/docs/aa-01567
• https://lists.debian.org/debian-lts-announce/2018/03/msg00015.html
• https://usn.ubuntu.com/3586-1/
• https://usn.ubuntu.com/3586-2/
• https://www.debian.org/security/2018/dsa-4133
• http://www.securityfocus.com/bid/103188
• http://www.securitytracker.com/id/1040437
• https://access.redhat.com/errata/RHSA-2018:0469

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