DNSSEC Amplification Bypass in Unbound <=1.25.1 via Excessive Upstream Packets
CVE-2026-50045 Published on July 22, 2026
'max-global-quota' reset by DNSSEC validation restarts
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, a single client query for a deeply nested name under a DNSSEC-signed parent can cause Unbound to send more upstream packets per client query than the configured 'max-global-quota'. This effectively bypasses a security configuration that limits upstream amplification traffic.
Timeline
Issue reported by Kunjie Shang
NLnet Labs shares patch 39 days later.
Kunjie Shang verifies patch 1 day later.
Fixes released with version 1.25.2 36 days later.
Weakness Type
What is a Network Amplification Vulnerability?
The software does not sufficiently monitor or control transmitted network traffic volume, so that an actor can cause the software to transmit more traffic than should be allowed for that actor. In the absence of a policy to restrict asymmetric resource consumption, the application or system cannot distinguish between legitimate transmissions and traffic intended to serve as an amplifying attack on target systems. Systems can often be configured to restrict the amount of traffic sent out on behalf of a client, based on the client's origin or access level. This is usually defined in a resource allocation policy. In the absence of a mechanism to keep track of transmissions, the system or application can be easily abused to transmit asymmetrically greater traffic than the request or client should be permitted to.
CVE-2026-50045 has been classified to as a Network Amplification vulnerability or weakness.
Products Associated with CVE-2026-50045
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Affected Versions
NLnet Labs Unbound:- Version 1.22.0 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.