# CVE-2026-93009: dnsmasq out-of-bounds read in DHCPv6 FQDN parser

Source: https://junglewise.ai/threats/cve-2026-93009-a-flaw-was-found-in-dnsmasq-the-dhcpv6-client-hostname-parser-can  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-93009 · Severity: medium · CVSS 4.3 · Published 2026-10-29

dnsmasq is a lightweight DNS and DHCP server commonly deployed on routers and network devices. A flaw in its DHCPv6 hostname parser allows a local network attacker to trigger a one-byte read past the end of a crafted FQDN option using a single DHCPv6 packet. While the extra byte is not returned to the client or logged and no crash has been demonstrated, this could potentially leak adjacent memory on affected systems.

Technologies: [Dnsmasq](https://junglewise.ai/threats/technologies/x-dnsmasq).

## Quick answers

**Is CVE-2026-93009 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93009 being exploited in the wild.

**How severe is CVE-2026-93009?** Medium severity, with a CVSS score of 4.3, published 29 October 2026.

**Which products and versions are affected?** Dnsmasq 2.76 and later.

**Is there a fix for CVE-2026-93009?** No fixed version is recorded yet. If DHCPv6 is not required, do not configure any IPv6 dhcp-range. Alternatively, compile dnsmasq without DHCPv6 using COPTS=-DNO_DHCP6, or restrict dnsmasq to trusted interfaces using --interface=&lt;iface&gt;.</anigation>
<parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-29"}] If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-93009 attacked?** It is attacked from the adjacent network, in a hosted service.

**Am I affected by CVE-2026-93009?** Check whether you run Dnsmasq at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix


If DHCPv6 is not required, do not configure any IPv6 dhcp-range. Alternatively, compile dnsmasq without DHCPv6 using COPTS=-DNO_DHCP6, or restrict dnsmasq to trusted interfaces using --interface=&lt;iface&gt;.</anigation>
<parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-29"}]

## Technical details

The DHCPv6 client hostname parser in dnsmasq reads one byte past the end of a crafted FQDN option because it checks the next label length before confirming the pointer is still within the option boundary (CWE-125: out-of-bounds read). An unauthenticated attacker on the local network can trigger this via a single DHCPv6 packet. The read value is used only to decide whether parsing continues; dnsmasq versions 2.76 and later are affected if DHCPv6 is compiled in and configured.

## Affected products

- dnsmasq 2.76 and later

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-93009](https://access.redhat.com/security/cve/CVE-2026-93009)

## Related threats

- [dnsmasq heap out-of-bounds write in DNSSEC validator](https://junglewise.ai/threats/cve-2026-93011-a-flaw-was-found-in-dnsmasq-after-a-reduction-of-internal-domain)
- [dnsmasq TCP DNS connection pool exhaustion denial of service](https://junglewise.ai/threats/cve-2026-93007-a-flaw-was-found-in-dnsmasq-the-tcp-dns-service-uses-a-small)