The dnsmasq package version 2.85-17.el9_6.1 for Red Hat Enterprise Linux 9.6 Extended Update Support contains multiple security vulnerabilities. These include a heap buffer overflow triggered via NAME_ESCAPE expansion (CVE-2026-2291), an infinite loop in NSEC bitmap parsing (CVE-2026-4890), a heap out-of-bounds read caused by RRSIG rdlen underflow (CVE-2026-4891), a DHCPv6 client identifier buffer overflow in the helper process (CVE-2026-4892), and a broken ECS source validation bypass (CVE-2026-4893). Red Hat has issued an important security advisory (RHSA-2026:20589) that provides updated dnsmasq packages to address these vulnerabilities. The advisory applies to Red Hat Enterprise Linux 8 and 9 Extended Update Support variants across multiple architectures. No CVSS scores are provided in the advisory. No known exploits in the wild have been reported. The vendor advisory includes instructions for applying the update and references to the CVE details.

These vulnerabilities could allow an attacker to cause denial of service conditions (e.g., infinite loops), memory corruption (heap buffer overflow and out-of-bounds reads), and bypass of source validation mechanisms in dnsmasq. Such issues may lead to crashes or potentially enable further exploitation depending on the environment and usage of dnsmasq. The advisory rates the overall impact as Important (high severity). No known active exploitation has been reported at this time.

Red Hat has released updated dnsmasq packages that address these vulnerabilities. Users of affected versions (=2.85-17.el9_6.1) should apply the security update as described in Red Hat advisory RHSA-2026:20589 and the linked article https://access.redhat.com/articles/11258. Applying the official update is the recommended and effective mitigation. No alternative workarounds or temporary fixes are indicated in the advisory.