Unbound 1.7.0-1.25.1 BOGUS A/AAAA Spoofing Enables Unauth XFR
CVE-2026-50248 Published on July 22, 2026
BOGUS configured primary hostname accepted for XFR in auth/rpz zones
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.
Timeline
Issue reported by Qifan Zhang
NLnet Labs shares patch 24 days later.
Qifan Zhang verifies patch 4 days later.
Fixes released with version 1.25.2 39 days later.
Weakness Type
Insufficient Verification of Data Authenticity
The software does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
Products Associated with CVE-2026-50248
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Affected Versions
NLnet Labs Unbound:- Version 1.7.0 and below 1.25.2 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.