CVE-2026-54478

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

22/07/2026

Last modified:

24/07/2026

Description

In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a &#39;proxy-protocol-port&#39; interface with &#39;answer-cookie: yes&#39;, the RFC 9018 server-cookie SipHash is computed over the proxy&#39;s wire address instead of the PROXYv2-declared client. One server cookie obtained through a given proxy node therefore validates for every PROXYv2-declared source behind that node. On a UDP+proxy-protocol front, an off-path attacker can harvest one cookie with a single legitimate query, then replay it under any spoofed source and pass DNS Cookie checks that were deployed to defeat this in the first place.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N CVSS v3.1 Severity and Metrics:

Base Score: 3.70 LOW
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): Low
Availability (A): None

Base Score 3.x

3.70

Severity 3.x

LOW

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:a:nlnetlabs:unbound::::::::	1.18.0 (including)	1.25.2 (excluding)

To consult the complete list of CPE names with products and versions, see this page

References to Advisories, Solutions, and Tools

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-54478.txt