Vulnerability 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.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nlnetlabs | Unbound | >= 1.18.0, < 1.25.2 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-54478?
CVE-2026-54478 is a vulnerability with a CVSS score of 3.7 (LOW). 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 pr...
How severe is CVE-2026-54478?
CVE-2026-54478 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-54478?
Check the references section above for vendor advisories and patch information. Affected products include: Nlnetlabs Unbound.