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

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.

Exploitable from the adjacent network, without an account and without any user action; the impact on data or service is limited.

Attack vector

Adjacent network

Attack complexity

Low

Privileges required

None

Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Affected products and versions