CVE-2021-3448

dnsmasq: fixed outgoing port used when --server is used with an interface name

Published Apr 8, 2021 CVSS 3.1 · 4 Medium EPSS 2.3% KEV · Not listed
Description
A flaw was found in dnsmasq in versions before 2.85. When configured to use a specific server for a given network interface, dnsmasq uses a fixed port while forwarding queries. An attacker on the network, able to find the outgoing port used by dnsmasq, only needs to guess the random transmission ID to forge a reply and get it accepted by dnsmasq. This flaw makes a DNS Cache Poisoning attack much easier. The highest threat from this vulnerability is to data integrity.

Analysis

No analysis available yet

Remediation

No remediation available yet

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2021-26773 A flaw was found in dnsmasq in versions before 2.85. When configured to use a specific server for a given network interface, dnsmasq uses a fixed port while forwarding queries. An attacker on the network, able to find the outgoing port used by dnsmasq, only needs to guess the random transmission ID to forge a reply and get it accepted by dnsmasq. This flaw makes a DNS Cache Poisoning attack much easier. The highest threat from this vulnerability is to data integrity.
Ubuntu USN Ubuntu USN USN-4976-1 Dnsmasq vulnerability
Ubuntu USN Ubuntu USN USN-4976-2 Dnsmasq vulnerability
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Dec 3, 2025, 12:40 AM
Reserved
Mar 16, 2021, 12:00 AM
Status
Modified
Published
Apr 8, 2021, 11:15 PM
Modified
Jun 17, 2026, 4:05 AM
Severity
Moderate
Public date
Mar 12, 2021, 12:00 AM