USN-8268-1

Andrew S. Fasano, Royce M, and Hugo Martinez Ray discovered that Dnsmasq did not allocate the necessary space to store domain names in some contexts. An attacker could possibly use this issue to write out-of-bounds, and could cause a denial of service or execute arbitrary code. (CVE-2026-2291)

Royce M discovered that Dnsmasq could loop infinitely due to erroneously missing the window header. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-4890)

Royce M discovered that a maliciously crafted packet could cause Dnsmasq to report a negative length. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-4891)

Royce M and Asim Viladi Oglu Manizada discovered that certain configurations of Dnsmasq could write over the DHCPv6 CLID buffer within a privileged helper. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-4892)

Royce M discovered that certain configurations of Dnsmasq could bypass internal bounds checks. An attacker could possibly use this issue to permit malformed packets, and could cause a denial of service. (CVE-2026-4893)

Hugo Martinez discovered that Dnsmasq did not check the rdlen element of a record. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-5172)