A remote code execution and denial-of-service vulnerability (CVE-2026-6507, CVSS 7.5 HIGH) exists in Dnsmasq when configured with the `--dhcp-split-relay` option, triggered by a specially crafted BOOTREPLY packet. The vulnerability affects Dnsmasq version 2.92-1ubuntu0.3 on Ubuntu 26.04 LTS, and the fix is provided in the standard repository update for that package version.
Ubuntu Security Notices USN-8308-1 USN-8308-1: Dnsmasq vulnerability Publication date 26 May 2026 Overview Dnsmasq could be made to crash or run programs if it received specially crafted network traffic. Releases 26.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Packages dnsmasq - Small caching DNS proxy and DHCP/TFTP server Details It was discovered that Dnsmasq incorrectly handled BOOTREPLY packets when configured with the --dhcp-split-relay option. A remote attacker could use this issue to cause Dnsmasq to crash, resulting in a denial of service, or possibly execute arbitrary code. It was discovered that Dnsmasq incorrectly handled BOOTREPLY packets when configured with the --dhcp-split-relay option. A remote attacker could use this issue to cause Dnsmasq to crash, resulting in a denial of service, or possibly execute arbitrary code. Update instructions In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 26.04 LTS resolute dnsmasq – 2.92-1ubuntu0.3 Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-6507 CVE-2026-6507