CVE-2026-54478
LOW
INFO
Priority: 0.01
BB Relevance:
57/100
Published: 2026-07-22
Modified: 2026-10-24
First seen: 2026-10-29
Status: active
Attack Surface
Network
No Auth
No Interaction
CVSS Vector Breakdown
AV:
Network
AC:
High
PR:
None
UI:
None
S:
Unchanged
C:
None
I:
Low
A:
None
Description
In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a 'proxy-protocol-port' interface with 'answer-cookie: yes', the RFC 9018 server-cookie SipHash is computed over the proxy'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.
Weakness Classification (1)
References & Advisories (1)
Vendor Advisory