CVE-2026-54478
DNS Cookie bypass when combined with proxy-protocol use
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-290 |
| Vendor | nlnet labs |
| Product | unbound |
| Published | Jul 22, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
Affected Versions
NLnet Labs / Unbound
1.18.0 < 1.25.2
References
Credits
Qifan Zhang (Palo Alto Networks)