RHSA-2026:20589 - Security Advisory

Topic

An update for dnsmasq is now available for Red Hat Enterprise Linux 8.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

The dnsmasq packages contain Dnsmasq, a lightweight DNS (Domain Name Server) forwarder and DHCP (Dynamic Host Configuration Protocol) server.

Security Fix(es):

• dnsmasq: dnsmasq: heap buffer overflow in cache via NAME_ESCAPE expansion (CVE-2026-2291)
• dnsmasq: NSEC bitmap parsing infinite loop (CVE-2026-4890)
• dnsmasq: RRSIG rdlen underflow leading to heap OOB read (CVE-2026-4891)
• dnsmasq: DHCPv6 CLID buffer overflow in helper process (CVE-2026-4892)
• dnsmasq: Broken ECS source validation bypass (CVE-2026-4893)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux for x86_64 8 x86_64
• Red Hat Enterprise Linux for IBM z Systems 8 s390x
• Red Hat Enterprise Linux for Power, little endian 8 ppc64le
• Red Hat Enterprise Linux for ARM 64 8 aarch64
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 8.10 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 8.10 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 8.10 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 8.10 s390x

Fixes

• BZ - 2439088 - CVE-2026-2291 dnsmasq: dnsmasq: heap buffer overflow in cache via NAME_ESCAPE expansion
• BZ - 2458516 - CVE-2026-4890 dnsmasq: NSEC bitmap parsing infinite loop
• BZ - 2458517 - CVE-2026-4891 dnsmasq: RRSIG rdlen underflow leading to heap OOB read
• BZ - 2458518 - CVE-2026-4892 dnsmasq: DHCPv6 CLID buffer overflow in helper process
• BZ - 2458519 - CVE-2026-4893 dnsmasq: Broken ECS source validation bypass

CVEs

• CVE-2026-2291
• CVE-2026-4890
• CVE-2026-4891
• CVE-2026-4892
• CVE-2026-4893

References

• https://access.redhat.com/security/updates/classification/#important