# CVE-2026-93009: Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder

Status: published. Published: 2026-10-29. Updated: 2026-11-04.

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

- 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>. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Ceph Storage 9 (rhceph/alloy-rhel10): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift4/ose-baremetal-runtimecfg-rhel8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift4/ose-baremetal-runtimecfg-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift5/ose-baremetal-runtimecfg-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenStack Platform 13 (Queens) (dnsmasq): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenStack Platform 18.0 (rhoso-operators/infra-rhel9-operator): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 4.3 (medium); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.20% as of 2026-11-03; percentile 10.26%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-93009 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2536083 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-93009; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-93009; retrieved 2026-11-04; source updated Not reported

Revision: bd4d0fea07a36c239b75d3de1f3ba6dc1a2c0a142d1750d36514b79a0fae6d3d

Canonical: https://y2.dev/cve/CVE-2026-93009

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