---
id: CVE-2026-93009
title: 'Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder'
summary: >-
  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 l…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
cvssSource: cna
cwe:
  - CWE-125
vendor: Red Hat
product: rhceph/alloy-rhel10
affected:
  - rhceph/alloy-rhel10 (all versions)
  - dnsmasq (all versions)
  - dnsmasq (all versions)
  - dnsmasq (all versions)
  - dnsmasq (all versions)
  - dnsmasq (all versions)
  - openshift4/ose-baremetal-runtimecfg-rhel8 (all versions)
  - openshift4/ose-baremetal-runtimecfg-rhel9 (all versions)
  - openshift/ose-rhel-coreos-8 (all versions)
  - openshift/ose-rhel-coreos-9 (all versions)
  - openshift5/ose-baremetal-runtimecfg-rhel9 (all versions)
  - openshift/ose-rhel-coreos-9 (all versions)
  - dnsmasq (all versions)
  - rhoso-operators/infra-rhel9-operator (all versions)
published: '2026-10-29'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T08:05:48.784Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-93009'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-93009'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2536083'
    label: RHBZ#2536083
tags:
  - cve.org
epss: 0.00202
epssPercentile: 0.10211
ingestedAt: '2026-11-03T10:42:03.632Z'
---

## Overview

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.

## Affected

- `rhceph/alloy-rhel10 (all versions)`
- `dnsmasq (all versions)`
- `dnsmasq (all versions)`
- `dnsmasq (all versions)`
- `dnsmasq (all versions)`
- `dnsmasq (all versions)`
- `openshift4/ose-baremetal-runtimecfg-rhel8 (all versions)`
- `openshift4/ose-baremetal-runtimecfg-rhel9 (all versions)`
- `openshift/ose-rhel-coreos-8 (all versions)`
- `openshift/ose-rhel-coreos-9 (all versions)`
- `openshift5/ose-baremetal-runtimecfg-rhel9 (all versions)`
- `openshift/ose-rhel-coreos-9 (all versions)`
- `dnsmasq (all versions)`
- `rhoso-operators/infra-rhel9-operator (all versions)`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

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>.