Out-of-bounds write in Dnsmasq - CVE-2026-2291

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Main Vulnerability Database Vulnerabilities #VU131139

Out-of-bounds write in Dnsmasq - CVE-2026-2291

Published: May 12, 2026


Vulnerability identifier: #VU131139
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-2291
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to out-of-bounds write in struct bigname when processing DNS queries or DNS responses containing large domain names. A remote attacker can send a specially crafted DNS query or response to cause a denial of service.


Affected software

Dnsmasq
Gentoo Linux
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
Debian Linux
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Enterprise Micro
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Ubuntu
Basesystem Module
openSUSE Leap
openEuler
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
net-dns/dnsmasq
dnsmasq (Ubuntu package)
dnsmasq
dnsmasq-debugsource
dnsmasq-debuginfo
dnsmasq-utils
dnsmasq (Red Hat package)
dnsmasq-help
dnsmasq-doc
dnsmasq-langpack
dnsmasq (Debian package)
dnsmasq-utils-debuginfo

How to mitigate CVE-2026-2291

Install security update from vendor's website.

Dnsmasq - update to 2.92
net-dns/dnsmasq - update to 2.66
dnsmasq (Ubuntu package) - addressed in versions 2.68-1ubuntu0.2+esm5, 2.90-0ubuntu0.16.04.1+esm3, 2.90-0ubuntu0.18.04.1+esm3, 2.90-0ubuntu0.20.04.1+esm2, 2.90-0ubuntu0.22.04.3, 2.90-2ubuntu0.3, 2.91-1ubuntu0.2, 2.92-1ubuntu0.2
dnsmasq - addressed in versions 2.78-18.24.1, 2.90-150100.7.34.1, 2.90-150400.16.9.1
dnsmasq-debugsource - addressed in versions 2.78-18.24.1, 2.90-150100.7.34.1, 2.90-150400.16.9.1
dnsmasq-debuginfo - addressed in versions 2.78-18.24.1, 2.90-150100.7.34.1, 2.90-150400.16.9.1
dnsmasq-utils - addressed in versions 2.79-36, 2.90-2
dnsmasq - addressed in versions 2.79-36, 2.90-2
dnsmasq (Red Hat package) - addressed in versions 2.79-36.el8_10, 2.85-17.el9_6.1, 2.85-18.el9_8.1
dnsmasq-help - addressed in versions 2.82-21, 2.86-15, 2.90-8, 2.90-9
dnsmasq-debugsource - addressed in versions 2.82-21, 2.86-15, 2.90-8, 2.90-9
dnsmasq-debuginfo - addressed in versions 2.82-21, 2.86-15, 2.90-8, 2.90-9
dnsmasq - addressed in versions 2.82-21, 2.86-15, 2.90-8, 2.90-9
dnsmasq-doc - update to 2.90-2
dnsmasq-langpack - update to 2.90-2
dnsmasq (Debian package) - addressed in versions 2.90-4~deb12u2, 2.91-1+deb13u1
dnsmasq-utils-debuginfo - update to 2.90-150400.16.9.1
dnsmasq-utils - update to 2.90-150400.16.9.1

External References

Related Security Bulletins