Ubuntu 26.04 Dnsmasq Critical DoS Risk Advisory USN-8268-1 CVE-2026
Summary: Several security issues were fixed in Dnsmasq. Software Description: - dnsmasq: Small caching DNS proxy and DHCP/TFTP server Details: 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,
Summary: Several security issues were fixed in Dnsmasq. Software Description: - dnsmasq: Small caching DNS proxy and DHCP/TFTP server Details: 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,
The problem can be corrected by updating your system to the following package versions: Ubuntu 26.04 LTS dnsmasq 2.92-1ubuntu0.2 Ubuntu 25.10 dnsmasq 2.91-1ubuntu0.2 Ubuntu 24.04 LTS dnsmasq 2.90-2ubuntu0.3 Ubuntu 22.04 LTS dnsmasq 2.90-0ubuntu0.22.04.3 Ubuntu 20.04 LTS dnsmasq 2.90-0ubuntu0.20.04.1+esm2 Available with Ubuntu Pro Ubuntu 18.04 LTS dnsmasq 2.90-0ubuntu0.18.04.1+esm3 Available with Ubuntu Pro Ubuntu 16.04 LTS dnsmasq 2.90-0ubuntu0.16.04.1+esm3 Available with Ubuntu Pro Ubuntu 14.04 LTS dnsmasq 2.68-1ubuntu0.2+esm5 Available with Ubuntu Pro In general, a standard system update will make all the necessary changes.
The problem can be corrected by updating your system to the following package versions: Ubuntu 26.04 LTS dnsmasq 2.92-1ubuntu0.2 Ubuntu 25.10 dnsmasq 2.91-1ubuntu0.2 Ubuntu 24.04 LTS dnsmasq 2.90-2ubuntu0.3 Ubuntu 22.04 LTS dnsmasq 2.90-0ubuntu0.22.04.3 Ubuntu 20.04 LTS dnsmasq 2.90-0ubuntu0.20.04.1+esm2 Available with Ubuntu Pro Ubuntu 18.04 LTS dnsmasq 2.90-0ubuntu0.18.04.1+esm3 Available with Ubuntu Pro Ubuntu 16.04 LTS dnsmasq 2.90-0ubuntu0.16.04.1+esm3 Available with Ubuntu Pro Ubuntu 14.04 LTS dnsmasq 2.68-1ubuntu0.2+esm5 Available with Ubuntu Pro In general, a standard system update will make all the necessary changes.
CVE-2026-2291, CVE-2026-4890, CVE-2026-4891, CVE-2026-4892, CVE-2026-4893, CVE-2026-5172
The full story
This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.
