CVE-2026-93009

Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder

Published Oct 29, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
Description
A flaw was found in dnsmasq. The DHCPv6 client hostname parser can read one byte past the end of a crafted FQDN option because it checks the next label length before confirming the pointer is still inside the option. An attacker on the local network can trigger this with a single DHCPv6 packet. The extra byte is not returned to the client or logged, and no crash has been demonstrated.

Remediation

Vendor Workaround

The following measures reduce risk: 1. If DHCPv6 is not required, do not configure any IPv6 dhcp-range. 2. Compile without DHCPv6 using COPTS=-DNO_DHCP6 if IPv6 DHCP is not needed. 3. Restrict dnsmasq to trusted interfaces with --interface=<iface>.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
cpe:/a:redhat:enterprise_linux:10
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Dnsmasq
Dnsmasq dnsmasq
Red Hat
Red Hat enterprise Linux
Redhat openshift Container Platform
Redhat openstack Platform
Vendors & Products Dnsmasq
Dnsmasq dnsmasq
Red Hat
Red Hat enterprise Linux
Redhat openshift Container Platform
Redhat openstack Platform
Type Values Removed Values Added
CPEs cpe:/a:redhat:openshift:5
Type Values Removed Values Added
Description A flaw was found in dnsmasq. The DHCPv6 client hostname parser can read one byte past the end of a crafted FQDN option because it checks the next label length before confirming the pointer is still inside the option. An attacker on the local network can trigger this with a single DHCPv6 packet. The extra byte is not returned to the client or logged, and no crash has been demonstrated.
Title Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder
First Time appeared Redhat
Redhat ceph Storage
Redhat enterprise Linux
Redhat openshift
Redhat openstack
Weaknesses CWE-125
CPEs cpe:/a:redhat:ceph_storage:9
cpe:/a:redhat:openshift:4
cpe:/a:redhat:openstack:13
cpe:/a:redhat:openstack:18.0
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat ceph Storage
Redhat enterprise Linux
Redhat openshift
Redhat openstack
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}