CVE-2026-50248
Received Received - Intake

Unbound DNS XFR Spoofing via BOGUS Primary Hostname

Publication date: 2026-07-22

Last updated on: 2026-07-22

Assigner: NLnet Labs

Description
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname's A/AAAA record (no valid RRSIG required) becomes the zone's XFR primary and can replaces the entire zone/the resolver's entire response policy.

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Meta Information

Published
2026-07-22
Last Modified
2026-07-22
Generated
2026-07-22
AI Q&A
2026-07-22
EPSS Evaluated
N/A
NVD
CVE-2026-50248
EUVD
EUVD-2026-47674

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
nlnet_labs unbound From 1.7.0 (inc) to 1.25.1 (inc)
nlnet_labs unbound 1.25.2

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-345 The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.

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Executive Summary

CVE-2026-50248 affects Unbound DNS software versions 1.7.0 to 1.25.1. When an auth/rpz zone has a primary hostname that resolves to a BOGUS A/AAAA record, the BOGUS hostname is still treated as a valid XFR endpoint. This allows an attacker who spoofs the hostname's A/AAAA record to become the zone's XFR primary and replace the entire zone or resolver's response policy.

Detection Guidance

To detect this vulnerability, check if your Unbound DNS software version is between 1.7.0 and 1.25.1. Run the command 'unbound -V' to verify the version. If the output shows a version in this range, your system is potentially vulnerable.

Impact Analysis

An attacker could manipulate DNS responses by replacing the zone or response policy, leading to incorrect or malicious domain resolutions. This could cause service disruptions, unauthorized access, or exposure to malicious content for users relying on the vulnerable Unbound resolver.

Compliance Impact

This vulnerability could lead to unauthorized data exposure or manipulation of DNS responses, potentially violating confidentiality and integrity requirements in GDPR and HIPAA. Organizations using affected Unbound versions may face compliance risks due to potential data breaches or unauthorized access.

Mitigation Strategies

Immediately upgrade Unbound to version 1.25.2 or later. If upgrading is not possible, apply the manual patch provided by NLnet Labs. Ensure no auth/rpz zones have primary hostnames resolving to BOGUS A/AAAA records.

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