Ubuntu USN · USN-8268-1

Dnsmasq vulnerabilities

Published: Tue, 12 May 2026 09:23

CVE-2026-4892CVE-2026-5172CVE-2026-4890CVE-2026-2291CVE-2026-4891CVE-2026-4893

Summary

Several security issues were fixed in Dnsmasq.

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, 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)

Recommended actions per Ubuntu release

StackPatch playbook auto-generated per release codename and per affected package.

Ubuntu bionic

dnsmasq→2.90-0ubuntu0.18.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.18.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.90-0ubuntu0.18.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.18.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.90-0ubuntu0.18.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.18.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.90-0ubuntu0.18.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.18.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.90-0ubuntu0.18.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.18.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu focal

dnsmasq→2.90-0ubuntu0.20.04.1+esm2apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.20.04.1+esm2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.90-0ubuntu0.20.04.1+esm2apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.20.04.1+esm2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.90-0ubuntu0.20.04.1+esm2apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.20.04.1+esm2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.90-0ubuntu0.20.04.1+esm2apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.20.04.1+esm2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.90-0ubuntu0.20.04.1+esm2apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.20.04.1+esm2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu jammy

dnsmasq→2.90-0ubuntu0.22.04.3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.22.04.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.90-0ubuntu0.22.04.3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.22.04.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.90-0ubuntu0.22.04.3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.22.04.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.90-0ubuntu0.22.04.3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.22.04.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.90-0ubuntu0.22.04.3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.22.04.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu noble

dnsmasq→2.90-2ubuntu0.3apt_upgrade
Standard apt upgrade. Install 2.90-2ubuntu0.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.90-2ubuntu0.3apt_upgrade
Standard apt upgrade. Install 2.90-2ubuntu0.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.90-2ubuntu0.3apt_upgrade
Standard apt upgrade. Install 2.90-2ubuntu0.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.90-2ubuntu0.3apt_upgrade
Standard apt upgrade. Install 2.90-2ubuntu0.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.90-2ubuntu0.3apt_upgrade
Standard apt upgrade. Install 2.90-2ubuntu0.3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu questing

dnsmasq→2.91-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.91-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.91-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.91-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.91-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.91-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.91-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.91-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.91-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.91-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu resolute

dnsmasq→2.92-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.92-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.92-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.92-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.92-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.92-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.92-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.92-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.92-1ubuntu0.2apt_upgrade
Standard apt upgrade. Install 2.92-1ubuntu0.2 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu trusty

dnsmasq→2.68-1ubuntu0.2+esm5apt_upgrade
Standard apt upgrade. Install 2.68-1ubuntu0.2+esm5 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.68-1ubuntu0.2+esm5apt_upgrade
Standard apt upgrade. Install 2.68-1ubuntu0.2+esm5 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.68-1ubuntu0.2+esm5apt_upgrade
Standard apt upgrade. Install 2.68-1ubuntu0.2+esm5 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.68-1ubuntu0.2+esm5apt_upgrade
Standard apt upgrade. Install 2.68-1ubuntu0.2+esm5 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

Ubuntu xenial

dnsmasq→2.90-0ubuntu0.16.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.16.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq→2.90-0ubuntu0.16.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.16.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base→2.90-0ubuntu0.16.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.16.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-base-lua→2.90-0ubuntu0.16.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.16.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-base-lua
```
Most apt upgrades restart their service automatically. needrestart lists anything else.
dnsmasq-utils→2.90-0ubuntu0.16.04.1+esm3apt_upgrade
Standard apt upgrade. Install 2.90-0ubuntu0.16.04.1+esm3 from the apt repo.
```
sudo apt-get update
sudo apt-get install --only-upgrade -y dnsmasq-utils
```
Most apt upgrades restart their service automatically. needrestart lists anything else.

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