CVE-2026-47703

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DNS Cache Poisoning in AdGuard Home via DoQ

Publication date: 2026-07-15

Last updated on: 2026-07-30

Assigner: GitHub, Inc.

Description

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

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Meta Information

Published

2026-07-15

Last Modified

2026-07-30

Generated

2026-08-05

AI Q&A

2026-07-16

EPSS Evaluated

2026-08-03

NVD

CVE-2026-47703

EUVD

EUVD-2026-44710

Affected Vendors & Products

Vendor	Product	Version / Range
adguard	adguardhome	to 0.107.75 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-346	The product does not properly verify that the source of data or communication is valid.
CWE-330	The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Attack-Flow Graph

Executive Summary

This vulnerability affects AdGuard Home's DoQ-to-UDP forwarding path. It causes the DNS ID to collapse to zero for every client-triggered query, reducing the backend tuple entropy from (txid, source-port) to just source-port. This creates a state exposure that allows an attacker to exploit an ICMP source-port oracle to distinguish correct backend UDP source ports from incorrect ones.

Detection Guidance

Detecting this vulnerability requires checking if your AdGuard Home instance is running a vulnerable version (v0.107.74 or earlier). Use the command 'adguardhome --version' to check the installed version. If the version is below 0.107.75, the system is vulnerable.

Impact Analysis

An attacker could exploit this to manipulate DNS responses, potentially causing incorrect or empty answers, steering queries to fallback upstreams, or forcing additional backend queries. This could lead to service disruptions or incorrect DNS resolution for users relying on AdGuard Home.

Compliance Impact

This vulnerability could compromise data integrity and confidentiality by allowing attackers to intercept or manipulate DNS traffic. This may violate requirements for secure data handling and transmission in GDPR and HIPAA, potentially leading to non-compliance.

Mitigation Strategies

Upgrade AdGuard Home to version 0.107.75 or later immediately. This version includes the patch for the DoQ-to-UDP forwarding path vulnerability. No other immediate steps are specified in the provided context.

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