Executive brief
A security vulnerability exists in dnsmasq, a widely used tool for providing network services like DNS and DHCP to local networks. An attacker on the same network can send a specially crafted request that causes the software to crash or allows them to take full control of the underlying system with administrative privileges. This could lead to a complete compromise of the device, potentially affecting network traffic routing and security for all connected users.
Technical details
A heap-based buffer overflow (CWE-122) exists in the DHCPv6 implementation of dnsmasq, specifically within the DHCP helper component. When the '--dhcp-script' configuration is enabled, the software fails to properly validate the length of hex-encoded DHCPv6 client identifiers. While these identifiers can be up to 65,535 bytes, they are written into a fixed 5,131-byte buffer in a process running with root privileges. An attacker on the local network or adjacent segment can exploit this by sending a crafted DHCPv6 packet to trigger an out-of-bounds write, leading to remote code execution as root. The vulnerability is addressed in dnsmasq version 2.92rel2 and Pi-hole FTL v6.6.2.
Affected products
- dnsmasq dnsmasq < 2.92rel2
- Red Hat Red Hat Enterprise Linux 6, 7, 8, 9, 10
- Red Hat OpenShift Container Platform 4
- Pi-hole FTL < 6.6.2
Timeline
- 2026-05-11: disclosed
- 2026-05-11: patched: Fixed in dnsmasq 2.92rel2 and Pi-hole FTL v6.6.2
- 2026-05-11: advisory
References
- https://github.com/NixOS/nixpkgs/pull/519082
- https://github.com/NixOS/nixpkgs/pull/519093
- https://github.com/pi-hole/FTL/releases/tag/v6.6.2
- https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2026q2/018471.html
- https://thekelleys.org.uk/dnsmasq/CVE/
- https://www.kb.cert.org/vuls/id/471747
- https://access.redhat.com/errata/RHSA-2026:19158