---
id: "CVE-2026-93009"
kind: "vulnerability"
aliases: ["CVE-2026-93009"]
title: "dnsmasq: DHCPv6 hostname parser reads one byte past buffer"
severity: "medium"
cvss: 4.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["dhcpv6", "dnsmasq", "linux", "package", "routers", "self-hosted"]
not_affected_if: ["managed-hosting", "no-dhcpv6"]
published_at: "2026-10-29T14:18:00+00:00"
first_seen_at: "2026-10-29T14:25:23+00:00"
updated_at: "2026-10-29T14:26:18+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93009", "first_seen_at": "2026-10-29T14:25:23+00:00"}]
---

# dnsmasq: DHCPv6 hostname parser reads one byte past buffer

dnsmasq's DHCPv6 client hostname parser can read one byte beyond the end of a crafted FQDN option because it checks a label length before confirming the pointer is still inside the option. An attacker on the local network can trigger the out-of-bounds read with a single DHCPv6 packet, but the extra byte is not returned or logged and no crash has been demonstrated.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `dnsmasq --version` to see the installed version.
- Check whether DHCPv6 is enabled in the dnsmasq configuration (a `dhcp-range` line with IPv6 addresses).

## Timeline

- 2026-10-29T14:25:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93009

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_